UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM N-CSR

CERTIFIED SHAREHOLDER REPORT OF REGISTERED

MANAGEMENT INVESTMENT COMPANIES

Investment Company Act file number 811-01466

Pioneer Fund

(Exact name of registrant as specified in charter)

60 State Street, Boston, MA 02109

(Address of principal executive offices) (ZIP code)

Terrence J. Cullen, Amundi Pioneer Asset Management, Inc.,

60 State Street, Boston, MA 02109

(Name and address of agent for service)

Registrant’s telephone number, including area code: (617) 742-7825

Date of fiscal year end: December 31, 2020

Date of reporting period: January 1, 2020 through June 30, 2020

Form N-CSR is to be used by management investment companies to file reports with the Commission not later than 10 days after the transmission to stockholders of any report that is required to be transmitted to stockholders under Rule 30e-1 under the Investment Company Act of 1940 (17 CFR 270.30e-1). The Commission may use the information provided on Form N-CSR in its regulatory, disclosure review, inspection, and policymaking roles.

A registrant is required to disclose the information specified by Form N-CSR, and the Commission will make this information public. A registrant is not required to respond to the collection of information contained in Form N-CSR unless the Form displays a currently valid Office of Management and Budget (“OMB”) control number. Please direct comments concerning the accuracy of the information collection burden estimate and any suggestions for reducing the burden to Secretary, Securities and Exchange Commission, 450 Fifth Street, NW, Washington, DC 20549-0609. The OMB has reviewed this collection of information under the clearance requirements of 44 U.S.C. ss. 3507.

Pioneer Fund

Semiannual Report | June 30, 2020

Ticker Symbols:

Class A	PIODX
Class C	PCODX
Class K	PIOKX
Class R	PIORX
Class Y	PYODX

Beginning in February 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s shareholder reports like this one will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or from your financial intermediary, such as a broker-dealer, bank or insurance company. Instead, the reports will be made available on the Fund’s website, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications electronically by contacting your financial intermediary or, if you invest directly with the Fund, by calling 1-800-225-6292.

You may elect to receive all future reports in paper free of charge. If you invest directly with the Fund, you can inform the Fund that you wish to continue receiving paper copies of your shareholder reports by calling 1-800-225-6292. If you invest through a financial intermediary, you can contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. Your election to receive reports in paper will apply to all funds held in your account if you invest through your financial intermediary or all funds held within the Pioneer Fund complex if you invest directly.

visit us: www.amundipioneer.com/us

Table of Contents

President’s Letter	2

Portfolio Management Discussion	4

Portfolio Summary	10

Prices and Distributions	11

Performance Update	12

Comparing Ongoing Fund Expenses	17

Schedule of Investments	19

Financial Statements	23

Notes to Financial Statements	32

Statement Regarding Liquidity Risk Management Program	42

Trustees, Officers and Service Providers	44

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President’s Letter

Dear Shareholders,

The new decade has arrived delivering a half-year that will go down in the history books. The beginning of 2020 seemed to extend the positive market environment of 2019. Then, March roared in like a lion and the COVID-19 pandemic became a global crisis impacting lives and life as we know it. The long-term impact on the global economy from the COVID-19 virus pandemic, while currently unknown, is likely to be considerable. It is clear that several industries have already felt greater effects than others. And the markets, which do not thrive on uncertainty, have been volatile, delivering significantly negative performance in the first quarter, and then staging a strong rally in the opening weeks of the second quarter. Our business continuity plan was implemented given the new COVID-19 guidelines, and most of our employees are working remotely. To date, our operating environment has faced no interruption. I am proud of the careful planning that has taken place and confident we can maintain this environment for as long as is prudent. History in the making for a company that first opened its doors way back in 1928.

Since 1928, Amundi Pioneer’s investment process has been built on a foundation of fundamental research and active management, principles which have guided our investment decisions for more than 90 years. We believe active management – that is, making active investment decisions – can help mitigate the potential risks during periods of market volatility. As the first several months of 2020 have reminded us, investment risk can arise from a number of factors in today’s global economy, including slower or stagnating growth, changing U.S. Federal Reserve policy, oil price shocks, political and geopolitical factors and, unfortunately, major public health concerns such as a viral pandemic.

At Amundi Pioneer, active management begins with our own fundamental, bottom-up research process. Our team of dedicated research analysts and portfolio managers analyzes each security under consideration, communicating directly with the management teams of the companies issuing the securities and working together to identify those securities that best meet our investment criteria for our family of funds. Our risk management approach begins with each and every security, as we strive to carefully understand the potential opportunity, while considering any and all risk factors.

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Today, as investors, we have many options. It is our view that active management can serve shareholders well, not only when markets are thriving, but also during periods of market stress. As you consider your long-term investment goals, we encourage you to work with your financial advisor to develop an investment plan that paves the way for you to pursue both your short-term and long-term goals.

We remain confident that the current crisis, like others in human history, will pass, and we greatly appreciate the trust you have placed in us and look forward to continuing to serve you in the future.

Sincerely,

Lisa M. Jones

Head of the Americas, President and CEO of U.S.

Amundi Pioneer Asset Management USA, Inc.

June 30, 2020

Any information in this shareowner report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

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Portfolio Management Discussion | 6/30/20

In the following discussion, Jeff Kripke discusses the market environment during the six-month period ended June 30, 2020, and Pioneer Fund’s performance during the period. Mr. Kripke, a senior vice president and a portfolio manager at Amundi Pioneer Asset Management, Inc. (Amundi Pioneer), is responsible for the day-to-day management of the Fund, along with James Yu, a vice president and associate portfolio manager at Amundi Pioneer, Craig Sterling, Managing Director, Director of Core Equity and Director of Equity Research, U.S., and a portfolio manager at Amundi Pioneer, and John Carey, Managing Director, Director of Equity Income, U.S., and a portfolio manager at Amundi Pioneer.

Q How did the Fund perform over the six-month period ended June 30, 2020?

A Pioneer Fund’s Class A shares returned -0.01% at net asset value during the six-month period ended June 30, 2020, while the Fund’s benchmark, the Standard & Poor’s 500 Index (the S&P 500), returned -3.08%. During the same six-month period, the average return of the 1,414 mutual funds in Morningstar’s Large Blend Funds category was -5.48%.

Q How would you describe the market environment for equities during the six-month period ended June 30, 2020?

A U.S. equities, while posting a negative return in the first half of 2020 as measured by the Fund’s benchmark, the S&P 500, nonetheless closed the six-month period on a high note, returning more than 20% during the second calendar quarter of the year (April through June).

The six-month period started off well, with healthy gains in the equity market from January through mid-February, as investor sentiment received a boost from solid economic and employment data and the news that China and the U.S. had agreed on a Phase One trade agreement, which was indicative of at least a slight thaw in the trade war between the two countries that had dominated financial headlines during 2019.

Then, stocks suffered a large, protracted slump beginning in the latter part of February as the COVID-19 virus spread from China into most other countries, including the U.S. Efforts to contain or at least slow the rate of COVID-19 infections resulted in the implementation of social-distancing guidelines and “lockdowns” imposed by state and local governments, which resulted in, among other things, the cancellation of all professional and amateur/collegiate sporting events and other large public gatherings, such as concerts, as well as the shuttering of businesses deemed non-essential.

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The containment measures slowed commerce (with the exception of e-commerce) to a crawl, and while a number of U.S. workers were able to keep their jobs by working remotely, much of the domestic economy ground to a halt during March and April, and the unemployment rate soared. The economic damage wrought by COVID-19 was deep and immediate, with the travel and restaurant industries hit hardest as people stayed at home.

U.S. stocks hit their low on March 23, and a liquidity “freeze” rattled the market for riskier fixed-income assets. At that point, the markets began to regain ground thanks to the combination of monetary and fiscal stimulus provided by the U.S. Federal Reserve (Fed) and the U.S. government. The Fed reduced the target range of the federal funds rate to zero, dusted off its 2008/2009 financial crisis playbook by expanding its balance sheet, and implemented new lending facilities, all of which helped bolster investors’ confidence. In addition, the U.S. Congress and the White House approved $2 trillion in fiscal stimulus designed to provide financial assistance to individuals and businesses in need. Other stimulus spending packages from the government came to fruition during the second quarter, and the unprecedented level of support generated a sense of optimism that the economic pain, while severe, would be short-lived.

Moreover, as April turned to May, some U.S. states that had been less affected by the initial onslaught of the virus began re-opening for business, thus providing further impetus for market participants to come back off the sidelines and once again delve into riskier assets, such as equities. Some “new jobs” reports released during the second quarter also surprised to the upside. All of those factors helped the S&P 500 Index close the six-month period with only a narrow loss, despite analysts’ expectations for a sharp decline in domestic economic growth.

Though stimulus was a major driver of the S&P 500’s positive performance in the second half of the six-month period, the composition of the Fund’s benchmark also played a role. As growth stocks have outperformed value in recent years, the S&P 500 has tended to become more growth-oriented and concentrated. The top five stocks in the S&P 500 are all “big tech” and tech-related growth stocks and accounted for more than 21% of the benchmark’s value at period-end, a record level of concentration for the S&P 500.

Most sectors within the S&P 500 were in negative territory for the full six-month period, with information technology (up by 15%) and consumer discretionary (up by 7%) the only two sectors to finish with positive returns. Energy, which was down by more than 35%, was by far the worst performer in the S&P 500 for the six-month period as oil prices cratered in

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the first quarter and into April, for a number of reasons, including a price war between Saudi Arabia and Russia, depressed demand caused by the COVID-19 lockdowns, and oversupply. Oil prices, and the energy sector as a whole, did rebound in the second quarter, but not by nearly enough to make up for the first-quarter carnage. Financials, which returned -24%, was the S&P 500’s second-worst performer during the six-month period, as the low-interest-rate environment took its toll on several companies in the sector.

Q Which of your investment decisions either contributed positively to, or detracted from, the Fund’s benchmark-relative performance during the six-month period ended June 30, 2020?

A Sector allocation results were a positive factor for the Fund’s benchmark-relative returns over the six-month period. In particular, an underweight to the weak energy sector and an overweight to consumer discretionary, one of only two S&P 500 sectors to finish the period in positive territory, aided relative performance. We had underweighted the portfolio to energy primarily due to oil-price concerns, which turned out to be even worse than anticipated. Meanwhile, we had increased the Fund’s consumer discretionary holdings opportunistically as share prices declined in the big COVID-19-related sell-off in March, which helped boost benchmark-relative results as the market rallied in the second quarter.

Security selection also contributed positively to the Fund’s benchmark-relative results over the six-month period, with results in the consumer discretionary, consumer staples, information technology, and industrials sectors adding the most to relative performance.

On the negative side, an underweight to the top-performing information technology sector, driven by valuation concerns, detracted from the Fund’s benchmark-relative returns during the six-month period. Security selection results also lagged the S&P 500 in the energy, health care, and real estate sectors over the six-month period.

With regard to individual positions, the top positive contributors to the Fund’s benchmark-relative performance over the six-month period were NVIDIA, Amazon.com, and Home Depot.

NVIDIA, which manufactures graphic-processing units used in computer games, driverless cars, and data centers, performed well over the six-month period as the company reported better-than-expected financial results driven by strong data-center demand. Home improvement retail giant Home Depot was another positive contributor to benchmark-relative performance for the six-month period. Home Depot reported strong first-quarter comparable

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store sales growth, driven by a surge in online sales, which have become a more significant factor in the company’s overall sales numbers. Home Depot has continued to display a clear competitive edge in servicing the needs of professional contractors, and we believe the contractor portion of the business is likely to expand rapidly given the impending reconfiguration of offices, schools, and other public-gathering places to allow for greater social distancing in the wake of COVID-19. Amazon.com, one of the largest providers of e-commerce, cloud-computing, and digital-streaming services, is another company that has been benefiting from the COVID-19 quarantine measures, as many shoppers have moved into the online-purchasing world. Moreover, Amazon’s instant-video service has experienced an increase in sales. We believe those trends could continue and help generate positive returns for shareholders, especially since the company’s two highest-margin businesses, AWS (cloud) and advertising, have also been enjoying significant momentum.

Individual positions that detracted from the Fund’s benchmark-relative performance during the six-month period included Schlumberger, Wells Fargo, and Elanco Animal Health.

Oilfield services firm Schlumberger was a victim of the very rough environment for energy stocks over the six-month period, as most of the company’s clients reduced spending on oilfield services given the dramatic decline in oil prices and the supply/demand imbalance. Shares of Wells Fargo struggled during the six-month period as the company’s turnaround, which has included cost savings initiatives, has been taking longer than the market expected. In addition, while it was anticipated that Wells Fargo would announce some kind of dividend* cut, the cents-per-share reduction was far greater than projected estimates. That said, Wells Fargo is one of the few nationwide, “footprint” banks in the U.S., and we believe the company’s current issues are correctible. Finally, the portfolio’s position in Elanco Animal Health detracted from the Fund’s benchmark-relative performance during the six-month period after the company reported a drop in revenue, largely related to a decline in disease prevention and therapeutic medicines for companion animals, as pet owners refrained from going to veterinarians due to the COVID-19 situation. We believe Elanco’s revenues could increase once the economy fully reopens. The company is also on track to close its acquisition of Bayer’s animal health business (not a Fund holding), which we believe could increase the scale and scope of the overall business.

* Dividends are not guaranteed.

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Q Did the Fund have any exposure to derivatives during the six-month period ended June 30, 2020?

A No, the Fund had no exposure to derivatives during the six-month period.

Q Could you discuss the Fund’s commitment to environmental, social, and governance (ESG) investing?

A ESG refers to the three central factors in measuring the sustainability and ethical impact of an investment in a company or business. We have historically followed an ESG-friendly approach when building the Fund’s portfolio. We use specific screening criteria to exclude investments from the portfolio in companies that fail to meet certain ESG standards across all industries. Per the prospectus, the Fund generally will not invest in companies significantly involved in certain business activities, including but not limited to, the production of alcohol, tobacco products, and certain controversial military weapons, and the operation of coal mines, gambling casinos and other gaming businesses. In addition, we view the “governance” aspect of ESG as critically important, as we believe companies that take steps to better manage risk exposure than their competitors can help reduce volatility, which could lead to solid performance during more difficult periods for both the economy and the markets.

Q What is your outlook for equities as the Fund enters the second half of its fiscal year, and how would you characterize the portfolio’s current positioning?

A We believe the economy is beginning to recover – led by the regions least affected by COVID-19 – as the population withdraws in phases from the lockdowns. The nature of particular industries is likely to influence the breadth of the recovery, with some businesses such as travel, restaurants, and live entertainment lagging the overall economy. However, we believe the exceptionally prompt actions taken by U.S. fiscal and monetary authorities at the outset of the crisis could create a bridge for many consumers as well as small, mid, and large businesses to reengage with their activities, and help steepen the trajectory of the recovery from the economic devastation that has just occurred. However, if the trend of new virus diagnoses seen in some U.S. states as the summer progressed continues, that could stall the economic recovery, as it had already led to some states dialing back their re-openings as of the end of the six-month period.

In terms of current positioning, the Fund is overweight versus the S&P 500 in consumer discretionary, due to the sector’s exposure to online retail as well as to equities of leading global consumer brands. As mentioned earlier, we had added some of those leading brand names to the portfolio opportunistically in the first quarter as their stock prices fell on concerns

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that consumer spending would decline during the pandemic. We believe the new portfolio additions have the potential to survive over the long term, and could possibly gain market share during the current period of economic decline.

The Fund is underweight to energy versus the benchmark due to oil supply-and-demand concerns, and underweight to “bond proxy” sectors such as utilities, which could offer limited upside potential, in our view, due to high valuations. With respect to information technology, the portfolio is underweight versus the S&P 500 in the sector for stock-specific/valuation reasons, but is overweight to the technology-related communications services sector by a similar amount.

Please refer to the Schedule of Investments on pages 19–22 for a full listing of Fund securities.

All investments are subject to risk, including the possible loss of principal. In the past several years, financial markets have experienced increased volatility and heightened uncertainty. The market prices of securities may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political, or regulatory conditions, recessions, inflation, changes in interest or currency rates, lack of liquidity in the bond markets, the spread of infectious illness or other public health issues or adverse investor sentiment. These conditions may continue, recur, worsen or spread.

The Fund generally excludes corporate issuers that do not meet or exceed minimum ESG standards. Excluding specific issuers limits the universe of investments available to the Fund, which may mean forgoing some investment opportunities available to funds without similar ESG standards.

Before investing, consider the product’s investment objectives, risks, charges and expenses. Contact your advisor or Amundi Pioneer Asset Management, Inc., for a prospectus or summary prospectus containing this information. Read it carefully.

Any information in this shareholder report regarding market or economic trends or the factors influencing the Fund’s historical or future performance are statements of opinion as of the date of this report. Past performance is no guarantee of future results.

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Portfolio Summary | 6/30/20

10 Largest Holdings
(As a percentage of total investments)*

1.	Amazon.com, Inc.	6.05%
2.	Microsoft Corp.	5.68
3.	Apple, Inc.	5.47
4.	Alphabet, Inc.	5.11
5.	Visa, Inc.	5.02
6.	Verizon Communications, Inc.	4.59
7.	Union Pacific Corp.	4.02
8.	United Parcel Service, Inc., Class B	3.65
9.	Facebook, Inc.	3.62
10.	NVIDIA Corp.	3.56

*	Excludes temporary cash investments and all derivative contracts except for options purchased. The Fund is actively managed, and current holdings may be different. The holdings listed should not be considered recommendations to buy or sell any securities.

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Prices and Distributions \| 6/30/20

Net Asset Value per Share

Class	6/30/20	12/31/19
A	$29.46	$29.58
C	$24.79	$24.90
K*	$29.92	$30.04
R	$29.62	$29.74
Y	$29.92	$30.04

Distributions per Share: 1/1/20–6/30/20

	Net Investment	Short-Term	Long-Term
Class	Income	Capital Gains	Capital Gains
A	$0.1000	$ —	$ —
C	$0.0100	$ —	$ —
K	$0.1400	$ —	$ —
R	$0.0400	$ —	$ —
Y	$0.1400	$ —	$ —

Index Definition

The Standard & Poor’s 500 Index is an unmanaged, commonly used measure of the broad U.S. stock market. Index returns are calculated monthly, assume reinvestment of dividends and, unlike Fund returns, do not reflect any fees, expenses or sales charges. It is not possible to invest directly in an index.

The index defined here pertains to the “Value of $10,000 Investment” and “Value of $5 Million Investment” charts on pages 12–16.

* Class K shares commenced operations on December 30, 2019.

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Performance Update \| 6/30/20	Class A Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class A shares of Pioneer Fund at public offering price during the periods shown, compared to that of the Standard & Poor’s 500 Index.

Average Annual Total Returns
(As of June 30, 2020)
	Net	Public
	Asset	Offering	S&P
	Value	Price	500
Period	(NAV)	(POP)	Index
10 years	12.77%	12.11%	13.99%
5 years	11.15	9.84	10.73
1 year	10.15	3.82	7.51

Expense Ratio
(Per prospectus dated May 1, 2020)
Gross
1.04%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance data quoted represents past performance, which is no guarantee of future results. Investment return and principal value will fluctuate, and shares, when redeemed, may be worth more or less than their original cost.

NAV results represent the percent change in net asset value per share. POP returns reflect deduction of maximum 5.75% sales charge. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

Performance results reflect any applicable expense waivers in effect during the periods shown. Without such waivers Fund performance would be lower. Waivers may not be in effect for all funds. Certain fee waivers are contractual through a specified period. Otherwise, fee waivers can be rescinded at any time. See the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for a more current expense ratio.

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Performance Update \| 6/30/20	Class C Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class C shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor’s 500 Index.

Average Annual Total Returns
(As of June 30, 2020)
			S&P
	If	If	500
Period	Held	Redeemed	Index
10 years	11.89%	11.89%	13.99%
5 years	10.27	10.27	10.73
1 year	9.27	9.27	7.51

Expense Ratio
(Per prospectus dated May 1, 2020)
Gross
1.84%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class C shares held for less than one year are also subject to a 1% contingent deferred sales charge (CDSC). “If Held” results represent the percent change in net asset value per share. NAV returns would have been lower had sales charges been reflected. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for a more current expense ratio.

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Performance Update | 6/30/20

Class K Shares

Investment Returns

The mountain chart on the right shows the change in value of a $5 million investment made in Class K shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor’s 500 Index.

Average Annual Total Returns
(As of June 30, 2020)
	Net
	Asset	S&P
	Value	500
Period	(NAV)	Index
10 years	12.96%	13.99%
5 years	11.53	10.73
1 year	12.03	7.51

Expense Ratio
(Per prospectus dated May 1, 2020)
Gross
0.67%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

The performance shown for Class K shares for the period prior to the commencement of operations of Class K shares on December 30, 2019, is the net asset value performance of the Fund’s Class A shares, which has not been restated to reflect any differences in expenses, including Rule 12b-1 fees applicable to Class A shares. Since fees for Class A shares generally are higher than those of Class K shares, the performance of Class K shares prior to their inception on December 30, 2019, would have been higher than the performance shown. For the period beginning December 30, 2019, the actual performance of Class K shares is reflected. Class K shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for a more current expense ratio.

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Performance Update \| 6/30/20	Class R Shares

Investment Returns

The mountain chart on the right shows the change in value of a $10,000 investment made in Class R shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor’s 500 Index.

Average Annual Total Returns
(As of June 30, 2020)
	Net
	Asset	S&P
	Value	500
Period	(NAV)	Index
10 years	12.35%	13.99%
5 years	10.68	10.73
1 year	9.64	7.51

Expense Ratio
(Per prospectus dated May 1, 2020)
Gross
1.45%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class R shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for a more current expense ratio.

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Performance Update \| 6/30/20	Class Y Shares

Investment Returns

The mountain chart on the right shows the change in value of a $5 million investment made in Class Y shares of Pioneer Fund during the periods shown, compared to that of the Standard & Poor’s 500 Index.


Average Annual Total Returns
(As of June 30, 2020)
	Net
	Asset	S&P
	Value	500
Period	(NAV)	Index
10 years	13.10%	13.99%
5 years	11.42	10.73
1 year	10.42	7.51

Expense Ratio
(Per prospectus dated May 1, 2020)
Gross	Net
0.81%	0.70%

Call 1-800-225-6292 or visit www.amundipioneer.com/us for the most recent month-end performance results. Current performance may be lower or higher than the performance data quoted.

Class Y shares are not subject to sales charges and are available for limited groups of eligible investors, including institutional investors. All results are historical and assume the reinvestment of dividends and capital gains. Other share classes are available for which performance and expenses will differ.

The net expense ratio reflects the contractual expense limitation currently in effect through May 1, 2021, for Class Y shares. There can be no assurance that Amundi Pioneer will extend the expense limitation beyond such time. Please see the prospectus and financial statements for more information.

The performance table and graph do not reflect the deduction of fees and taxes that a shareowner would pay on Fund distributions or the redemption of Fund shares.

Please refer to the financial highlights for more current expense ratios.

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Comparing Ongoing Fund Expenses

As a shareowner in the Fund, you incur two types of costs:

(1)	ongoing costs, including management fees, distribution and/or service (12b-1) fees, and other Fund expenses; and
(2)	transaction costs, including sales charges (loads) on purchase payments.

This example is intended to help you understand your ongoing expenses (in dollars) of investing in the Fund and to compare these costs with the ongoing costs of investing in other mutual funds. The example is based on an investment of $1,000 at the beginning of the Fund’s latest six-month period and held throughout the six months.

Using the Tables

Actual Expenses

The first table below provides information about actual account values and actual expenses. You may use the information in this table, together with the amount you invested, to estimate the expenses that you paid over the period as follows:

(1)	Divide your account value by $1,000
	Example: an $8,600 account value ÷ $1,000 = 8.6
(2)	Multiply the result in (1) above by the corresponding share class’s number in the third row under the heading entitled “Expenses Paid During Period” to estimate the expenses you paid on your account during this period.

Expenses Paid on a $1,000 Investment in Pioneer Fund

Based on actual returns from January 1, 2020 through June 30, 2020.

Share Class	A	C	K	R	Y
Beginning Account	$1,000.00	$1,000.00	$1,000.00	$1,000.00	$1,000.00
Value on 1/1/20
Ending Account	$999.90	$996.10	$1,001.40	$997.60	$1,001.40
Value on 6/30/20
Expenses Paid	$5.22	$9.03	$3.43	$7.40	$3.63
During Period*

*	Expenses are equal to the Fund’s annualized expense ratio of 1.05%, 1.82%, 0.69%, 1.49%, and 0.73%, for Class A, Class C, Class K, Class R, and Class Y, respectively, multiplied by the average account value over the period, multiplied by 182/366 (to reflect the one-half year period).

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Hypothetical Example for Comparison Purposes

The table below provides information about hypothetical account values and hypothetical expenses based on the Fund’s actual expense ratio and an assumed rate of return of 5% per year before expenses, which is not the Fund’s actual return. The hypothetical account values and expenses may not be used to estimate the actual ending account balance or expenses you paid for the period.

You may use this information to compare the ongoing costs of investing in the Fund and other funds. To do so, compare this 5% hypothetical example with the 5% hypothetical examples that appear in the shareholder reports of the other funds.

Please note that the expenses shown in the tables are meant to highlight your ongoing costs only and do not reflect any transaction costs, such as sales charges (loads) that are charged at the time of the transaction. Therefore, the table below is useful in comparing ongoing costs only and will not help you determine the relative total costs of owning different funds. In addition, if these transaction costs were included, your costs would have been higher.

Expenses Paid on a $1,000 Investment in Pioneer Fund

Based on a hypothetical 5% per year return before expenses, reflecting the period from January 1, 2020 through June 30, 2020.

Share Class	A	C	K	R	Y
Beginning Account	$1,000.00	$1,000.00	$1,000.00	$1,000.00	$1,000.00
Value on 1/1/20
Ending Account	$1,019.64	$1,015.81	$1,021.43	$1,017.45	$1,021.23
Value on 6/30/20
Expenses Paid	$5.27	$9.12	$3.47	$7.47	$3.67
During Period*

*	Expenses are equal to the Fund’s annualized expense ratio of 1.05%, 1.82%, 0.69%, 1.49%, and 0.73%, for Class A, Class C, Class K, Class R, and Class Y, respectively, multiplied by the average account value over the period, multiplied by 182/366 (to reflect the one-half year period).

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Schedule of Investments | 6/30/20 (unaudited)

Shares		Value
	UNAFFILIATED ISSUERS — 98.7%
	COMMON STOCKS — 98.7% of Net Assets
	Air Freight & Logistics — 3.6%
1,690,386	United Parcel Service, Inc., Class B	$ 187,937,115
	Total Air Freight & Logistics	$ 187,937,115
	Banks — 6.1%
7,315,008	Bank of America Corp.	$ 173,731,440
5,740,496	Wells Fargo & Co.	146,956,698
	Total Banks	$ 320,688,138
	Beverages — 1.9%
1,630,036	Coca-Cola Co.	$ 72,830,008
198,849	PepsiCo., Inc.	26,299,769
	Total Beverages	$ 99,129,777
	Biotechnology — 1.6%
198,450(a)	Biogen, Inc.	$ 53,095,297
45,060(a)	Regeneron Pharmaceuticals, Inc.	28,101,669
	Total Biotechnology	$ 81,196,966
	Building Products — 1.1%
2,661,038	Carrier Global Corp.	$ 59,128,264
	Total Building Products	$ 59,128,264
	Capital Markets — 5.1%
127,752	BlackRock, Inc.	$ 69,508,586
655,777	CME Group, Inc.	106,589,993
265,517	S&P Global, Inc.	87,482,541
	Total Capital Markets	$ 263,581,120
	Chemicals — 2.4%
1,040,044	International Flavors & Fragrances, Inc.	$ 127,363,788
	Total Chemicals	$ 127,363,788
	Consumer Discretionary — 4.9%
1,429,750	NIKE, Inc., Class B	$ 140,186,988
1,560,865	Starbucks Corp.	114,864,055
	Total Consumer Discretionary	$ 255,051,043
	Diversified Telecommunication Services — 4.5%
4,294,344	Verizon Communications, Inc.	$ 236,747,185
	Total Diversified Telecommunication Services	$ 236,747,185
	Electric Utilities — 0.0%†
12,445	Eversource Energy	$ 1,036,295
	Total Electric Utilities	$ 1,036,295

The accompanying notes are an integral part of these financial statements.

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Schedule of Investments | 6/30/20 (unaudited) (continued)

Shares		Value
	Energy Equipment & Services — 1.3%
3,577,749	Schlumberger, Ltd.	$ 65,794,804
	Total Energy Equipment & Services	$ 65,794,804
	Entertainment — 2.0%
929,943	Walt Disney Co.	$ 103,697,944
	Total Entertainment	$ 103,697,944
	Financials — 0.4%
615,183	Charles Schwab Corp.	$ 20,756,274
	Total Financials	$ 20,756,274
	Food & Staples Retailing — 1.0%
437,838	Walmart, Inc.	$ 52,444,236
	Total Food & Staples Retailing	$ 52,444,236
	Food Products — 0.0%†
5,756	McCormick & Co., Inc.	$ 1,032,684
	Total Food Products	$ 1,032,684
	Health Care — 3.6%
741,234	Johnson & Johnson	$ 104,239,738
615,024	Zoetis, Inc.	84,282,889
	Total Health Care	$ 188,522,627
	Health Care Equipment & Supplies — 3.9%
798,869	Danaher Corp.	$ 141,264,005
683,864	Medtronic Plc	62,710,329
	Total Health Care Equipment & Supplies	$ 203,974,334
	Industrial Conglomerates — 0.4%
146,815	Honeywell International, Inc.	$ 21,227,981
	Total Industrial Conglomerates	$ 21,227,981
	Information Technology — 3.1%
553,987	Mastercard, Inc.	$ 163,813,956
	Total Information Technology	$ 163,813,956
	Insurance — 0.8%
1,029,743	Hartford Financial Services Group, Inc.	$ 39,696,593
	Total Insurance	$ 39,696,593
	Interactive Media & Services — 8.6%
185,782(a)	Alphabet, Inc.	$ 263,448,165
821,694(a)	Facebook, Inc.	186,582,057
	Total Interactive Media & Services	$ 450,030,222
	Internet & Direct Marketing Retail — 6.0%
113,027(a)	Amazon.com, Inc.	$ 311,821,148
	Total Internet & Direct Marketing Retail	$ 311,821,148

The accompanying notes are an integral part of these financial statements.

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Shares		Value
	IT Services — 5.0%
1,340,084	Visa, Inc.	$ 258,864,026
	Total IT Services	$ 258,864,026
	Life Sciences Tools & Services — 2.0%
1,196,594	Agilent Technologies, Inc.	$ 105,743,012
	Total Life Sciences Tools & Services	$ 105,743,012
	Machinery — 0.9%
855,793	Otis Worldwide Corp.	$ 48,660,390
	Total Machinery	$ 48,660,390
	Oil, Gas & Consumable Fuels — 0.0%†
10,586	EOG Resources, Inc.	$ 536,287
	Total Oil, Gas & Consumable Fuels	$ 536,287
	Pharmaceuticals — 3.7%
5,753,694(a)	Elanco Animal Health, Inc.	$ 123,416,736
932,473	Merck & Co., Inc.	72,108,137
	Total Pharmaceuticals	$ 195,524,873
	Road & Rail — 4.0%
1,226,000	Union Pacific Corp.	$ 207,279,820
	Total Road & Rail	$ 207,279,820
	Semiconductors & Semiconductor Equipment — 8.3%
754,958	Analog Devices, Inc.	$ 92,588,049
372,263	Lam Research Corp.	120,412,190
686,779(a)	Micron Technology, Inc.	35,382,854
482,550	NVIDIA Corp.	183,325,571
	Total Semiconductors & Semiconductor Equipment	$ 431,708,664
	Software — 5.6%
1,439,942	Microsoft Corp.	$ 293,042,596
	Total Software	$ 293,042,596
	Specialty Retail — 1.5%
306,528	Home Depot, Inc.	$ 76,788,329
	Total Specialty Retail	$ 76,788,329
	Technology Hardware, Storage & Peripherals — 5.4%
772,667	Apple, Inc.	$ 281,868,921
	Total Technology Hardware, Storage & Peripherals	$ 281,868,921
	TOTAL COMMON STOCKS
	(Cost $4,024,880,849)	$ 5,154,689,412
	TOTAL INVESTMENTS IN UNAFFILIATED ISSUERS — 98.7%
	(Cost $4,024,880,849)	$ 5,154,689,412
	OTHER ASSETS AND LIABILITIES — 1.3%	$ 69,051,671
	NET ASSETS — 100.0%	$ 5,223,741,083

The accompanying notes are an integral part of these financial statements.

Pioneer Fund | Semiannual Report | 6/30/20 21

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Schedule of Investments | 6/30/20 (unaudited) (continued)

†	Amount rounds to less than 0.1%.

(a)	Non-income producing security.

Purchases and sales of securities (excluding temporary cash investments) for the six months ended June 30, 2020, aggregated $2,499,769,224 and $2,650,064,250, respectively.

The Fund is permitted to engage in purchase and sale transactions (“cross trades”) with certain funds and accounts for which Amundi Pioneer Asset Management, Inc. (the “Adviser”) serves as the Fund’s investment adviser, as set forth in Rule 17a-7 under the Investment Company Act of 1940, pursuant to procedures adopted by the Board of Trustees. Under these procedures, cross trades are effected at current market prices. During the six months ended June 30, 2020, the Fund did not engage in any cross trade activity.

At June 30, 2020, the net unrealized appreciation on investments based on cost for federal tax purposes of $4,034,705,885 was as follows:

Aggregate gross unrealized appreciation for all investments in which
there is an excess of value over tax cost	$ 1,326,093,305
Aggregate gross unrealized depreciation for all investments in which
there is an excess of tax cost over value	(206,109,778)
Net unrealized appreciation	$ 1,119,983,527

Various inputs are used in determining the value of the Fund’s investments. These inputs are summarized in the three broad levels below.

Level 1 – quoted prices in active markets for identical securities.

Level 2 – other significant observable inputs (including quoted prices for similar securities, interest rates, prepayment speeds, credit risks, etc.). See Notes to Financial Statements — Note 1A.

Level 3 – significant unobservable inputs (including the Fund’s own assumptions in determining fair value of investments). See Notes to Financial Statements — Note 1A.

The following is a summary of the inputs used as of June 30, 2020, in valuing the Fund’s investments:

	Level 1		Level 2		Level 3		Total
Common Stocks	$	5,154,689,412	$	—	$	—	$	5,154,689,412
Total Investments
in Securities	$	5,154,689,412	$	—	$	—	$	5,154,689,412

During the six months ended June 30, 2020, there were no transfers between Levels 1, 2 and 3.

The accompanying notes are an integral part of these financial statements.

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Statement of Assets and Liabilities | 6/30/20 (unaudited)

ASSETS:
Investments in unaffiliated issuers, at value (cost $4,024,880,849)	$	5,154,689,412
Cash		46,942,083
Receivables —
Investment securities sold		62,631,465
Fund shares sold		1,553,624
Dividends		4,503,996
Interest		483,184
Due from the Adviser		256,212
Other assets		84,941
Total assets	$	5,271,144,917
LIABILITIES:
Payables —
Investment securities purchased	$	42,795,270
Fund shares repurchased		2,517,817
Distributions		55,470
Due to affiliates		835,637
Accrued expenses		1,199,640
Total liabilities	$	47,403,834
NET ASSETS:
Paid-in capital	$	3,827,339,904
Distributable earnings		1,396,401,179
Net assets	$	5,223,741,083
NET ASSET VALUE PER SHARE:
No par value (unlimited number of shares authorized)
Class A (based on $4,987,441,171/169,314,844 shares)	$	29.46
Class C (based on $38,250,442/1,542,939 shares)	$	24.79
Class K (based on $15,597,504/521,238 shares)	$	29.92
Class R (based on $43,561,418/1,470,835 shares)	$	29.62
Class Y (based on $138,890,548/4,641,994 shares)	$	29.92
MAXIMUM OFFERING PRICE PER SHARE:
Class A (based on $29.46 net asset value per share/100%-5.75%
maximum sales charge)	$	31.26

The accompanying notes are an integral part of these financial statements.

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Statement of Operations (unaudited)
FOR THE SIX MONTHS ENDED 6/30/20

INVESTMENT INCOME:
Dividends from unaffiliated issuers (net of foreign taxes
withheld $(479,928))	$	44,022,949
Interest from unaffiliated issuers		224,671
Total investment income				$	44,247,620
EXPENSES:
Management fees
Basic Fee	$	14,966,439
Performance adjustment		1,490,311
Administrative expense		908,850
Transfer agent fees
Class A		1,635,826
Class C		17,889
Class R		66,465
Class Y		57,247
Distribution fees
Class A		5,982,904
Class C		183,232
Class R		109,889
Shareowner communications expense		1,027,647
Custodian fees		42,733
Registration fees		54,727
Professional fees		118,710
Printing expense		21,049
Trustees’ fees		142,459
Insurance expense		852
Miscellaneous		84,647
Total expenses				$	26,911,876
Less fees waived and expenses reimbursed by the Adviser					(732,856	)
Net expenses				$	26,179,020
Net investment income				$	18,068,600
REALIZED AND UNREALIZED GAIN (LOSS) ON INVESTMENTS:
Net realized gain (loss) on:
Investments in unaffiliated issuers	$	217,868,140
Other assets and liabilities denominated in foreign currencies		(46,009	)	$	217,822,131
Change in net unrealized appreciation (depreciation) on:
Investments in unaffiliated issuers	$	(244,527,704	)
Other assets and liabilities denominated in foreign currencies		5,564		$	(244,522,140	)
Net realized and unrealized gain (loss) on investments				$	(26,700,009	)
Net decrease in net assets resulting from operations				$	(8,631,409	)

The accompanying notes are an integral part of these financial statements.

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Statements of Changes in Net Assets

	Six Months
	Ended			Year
	6/30/20			Ended
	(unaudited)			12/31/19
FROM OPERATIONS:
Net investment income (loss)	$	18,068,600		$	42,527,094
Net realized gain (loss) on investments		217,822,131			431,403,378
Change in net unrealized appreciation (depreciation)
on investments		(244,522,140	)		853,154,289
Net increase (decrease) in net assets resulting
from operations	$	(8,631,409	)	$	1,327,084,761
DISTRIBUTIONS TO SHAREOWNERS:
Class A ($0.10 and $2.77 per share, respectively)	$	(17,030,231	)	$	(448,927,608	)
Class C ($0.01 and $2.60 per share, respectively)		(15,588	)		(3,778,067	)
Class K* ($0.14 and $— per share, respectively)		(65,849	)		—
Class R ($0.04 and $2.65 per share, respectively)		(61,112	)		(4,021,211	)
Class Y ($0.14 and $2.84 per share, respectively)		(551,761	)		(10,568,673	)
Total distributions to shareowners	$	(17,724,541	)	$	(467,295,559	)
FROM FUND SHARE TRANSACTIONS:
Net proceeds from sales of shares	$	129,582,578		$	159,538,801
Reinvestment of distributions		17,056,114			450,232,304
Cost of shares repurchased		(250,537,794	)		(556,771,456	)
Net increase (decrease) in net assets resulting
from Fund share transactions	$	(103,899,102	)	$	52,999,649
Net increase (decrease) in net assets	$	(130,255,052	)	$	912,788,851
NET ASSETS:
Beginning of period	$	5,353,996,135		$	4,441,207,284
End of period	$	5,223,741,083		$	5,353,996,135

* Class K shares commenced operations on December 30, 2019.

The accompanying notes are an integral part of these financial statements.

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Statements of Changes in Net Assets (continued)

	Six Months			Six Months
	Ended			Ended
	6/30/20			6/30/20			Year Ended			Year Ended
	Shares			Amount			12/31/19			12/31/19
	(unaudited)			(unaudited)			Shares			Amount
Class A
Shares sold		2,337,045		$	64,874,992			3,485,400		$	98,927,373
Reinvestment of distributions		651,706			16,450,830			14,978,708			433,416,551
Less shares repurchased		(7,612,980	)		(212,110,627	)		(16,745,891	)		(478,351,232	)
Net increase/(decrease)		(4,624,229	)	$	(130,784,805	)		1,718,217		$	53,992,692
Class C
Shares sold		185,573		$	4,429,071			404,803		$	9,382,245
Reinvestment of distributions		795			15,398			152,823			3,720,891
Less shares repurchased		(255,383	)		(5,885,914	)		(700,501	)		(16,505,700	)
Net decrease		(69,015	)	$	(1,441,445	)		(142,875	)	$	(3,402,564	)
Class K
Shares sold		94,615		$	2,658,394			433,624		$	13,060,741
Reinvestment of distributions		2,521			65,849			—			—
Less shares repurchased		(9,522	)		(255,129	)		—			—
Net increase		87,614		$	2,469,114			433,624		$	13,060,741
Class R
Shares sold		136,032		$	3,601,753			120,796		$	3,475,278
Reinvestment of distributions		2,483			60,738			137,643			3,997,777
Less shares repurchased		(294,125	)		(8,144,334	)		(412,552	)		(11,918,875	)
Net decrease		(155,610	)	$	(4,481,843	)		(154,113	)	$	(4,445,820	)
Class Y
Shares sold		1,911,933		$	54,018,368			1,175,648		$	34,693,164
Reinvestment of distributions		17,746			463,299			309,414			9,097,085
Less shares repurchased		(875,702	)		(24,141,790	)		(1,699,094	)		(49,995,649	)
Net increase/(decrease)		1,053,977		$	30,339,877			(214,032	)	$	(6,205,400	)

The accompanying notes are an integral part of these financial statements.

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Financial Highlights

	Six Months
	Ended			Year			Year			Year			Year			Year
	6/30/20			Ended			Ended			Ended			Ended			Ended
	(unaudited)			12/31/19			12/31/18			12/31/17			12/31/16*			12/31/15*
Class A
Net asset value, beginning of period	$	29.58		$	24.76		$	28.81		$	28.90		$	31.92		$	36.67
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.10		$	0.25		$	0.29		$	0.31		$	0.35		$	0.31
Net realized and unrealized gain (loss) on investments		(0.12	)		7.34			(0.54	)		5.75			2.56			(0.42	)
Net increase (decrease) from investment operations	$	(0.02	)	$	7.59		$	(0.25	)	$	6.06		$	2.91		$	(0.11	)
Distributions to shareowners:
Net investment income	$	(0.10	)	$	(0.24	)	$	(0.28	)	$	(0.29	)	$	(0.34	)	$	(0.30	)
Net realized gain		—			(2.53	)		(3.52	)		(5.86	)		(5.59	)		(4.34	)
Total distributions	$	(0.10	)	$	(2.77	)	$	(3.80	)	$	(6.15	)	$	(5.93	)	$	(4.64	)
Net increase (decrease) in net asset value	$	(0.12	)	$	4.82		$	(4.05	)	$	(0.09	)	$	(3.02	)	$	(4.75	)
Net asset value, end of period	$	29.46		$	29.58		$	24.76		$	28.81		$	28.90		$	31.92
Total return (b)		(0.01	)%(c)		31.00	%		(1.74	)%		21.54	%(d)		9.60	%		(0.43	)%(e)
Ratio of net expenses to average net assets		1.05	%(f)		1.04	%		0.96	%		0.94	%		0.98	%		0.98	%
Ratio of net investment income (loss) to average net assets		0.73	%(f)		0.86	%		0.98	%		0.99	%		1.09	%		0.86	%
Portfolio turnover rate		50	%(c)		71	%		60	%		58	%		62	%		50	%
Net assets, end of period (in thousands)	$	4,987,441		$	5,144,683		$	4,264,175		$	4,765,993		$	4,426,909		$	4,402,310
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		1.08	%(f)		1.04	%		0.96	%		0.94	%		0.98	%		0.98	%
Net investment income (loss) to average net assets		0.70	%(f)		0.86	%		0.98	%		0.99	%		1.09	%		0.86	%

*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per share data presented above is based on the average shares outstanding for the period presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account.
(c)	Not annualized.
(d)	If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2017, the total return would have been 21.51%.
(e)	If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.46)%.
(f)	Annualized.

The accompanying notes are an integral part of these financial statements.

Pioneer Fund | Semiannual Report | 6/30/20 27

Table of Contents

Financial Highlights (continued)

	Six Months
	Ended			Year			Year			Year			Year			Year
	6/30/20			Ended			Ended			Ended			Ended			Ended
	(unaudited)			12/31/19			12/31/18			12/31/17			12/31/16*			12/31/15*
Class C
Net asset value, beginning of period	$	24.90		$	21.22		$	25.17		$	25.91		$	29.20		$	33.97
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	(0.01	)	$	0.01		$	0.04		$	0.05		$	0.09		$	0.02
Net realized and unrealized gain (loss) on investments		(0.09	)		6.27			(0.42	)		5.14			2.32			(0.39	)
Net increase (decrease) from investment operations	$	(0.10	)	$	6.28		$	(0.38	)	$	5.19		$	2.41		$	(0.37	)
Distributions to shareowners:
Net investment income	$	(0.01	)	$	(0.07	)	$	(0.05	)	$	(0.07	)	$	(0.11	)	$	(0.06	)
Net realized gain		—			(2.53	)		(3.52	)		(5.86	)		(5.59	)		(4.34	)
Total distributions	$	(0.01	)	$	(2.60	)	$	(3.57	)	$	(5.93	)	$	(5.70	)	$	(4.40	)
Net increase (decrease) in net asset value	$	(0.11	)	$	3.68		$	(3.95	)	$	(0.74	)	$	(3.29	)	$	(4.77	)
Net asset value, end of period	$	24.79		$	24.90		$	21.22		$	25.17		$	25.91		$	29.20
Total return (b)		(0.39	)%(c)		29.92	%		(2.52	)%		20.57	%		8.74	%		(1.23	)%(d)
Ratio of net expenses to average net assets		1.82	%(e)		1.84	%		1.76	%		1.73	%		1.77	%		1.76	%
Ratio of net investment income (loss) to average net assets		(0.04	)%(e)		0.05	%		0.15	%		0.19	%		0.30	%		0.07	%
Portfolio turnover rate		50	%(c)		71	%		60	%		58	%		62	%		50	%
Net assets, end of period (in thousands)	$	38,250		$	40,142		$	37,237		$	89,663		$	109,749		$	129,720
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		1.85	%(e)		1.84	%		1.76	%		1.73	%		1.77	%		1.76	%
Net investment income (loss) to average net assets		(0.07	)%(e)		0.05	%		0.15	%		0.19	%		0.30	%		0.07	%

*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per share data presented above is based on the average shares outstanding for the period presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions, the complete redemption of the investment at net asset value at the end of each period and no sales charges. Total return would be reduced if sales charges were taken into account.
(c)	Not annualized.
(d)	If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (1.26)%.
(e)	Annualized.

The accompanying notes are an integral part of these financial statements.

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	Six Months
	Ended
	6/30/20			12/30/19* to
	(unaudited)			12/31/19
Class K
Net asset value, beginning of period	$	30.04		$	30.12
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.16		$	0.00	(b)
Net realized and unrealized gain (loss) on investments		(0.14	)		(0.08	)
Net increase (decrease) from investment operations	$	0.02		$	(0.08	)
Distributions to shareowners:
Net investment income	$	(0.14	)	$	—
Total distributions	$	(0.14	)	$	—
Net increase (decrease) in net asset value	$	(0.12	)	$	(0.08	)
Net asset value, end of period	$	29.92		$	30.04
Total return (c)		0.14	%(d)		33.04	%(d)
Ratio of net expenses to average net assets		0.69	%(e)		0.67	%(e)
Ratio of net investment income (loss) to average net assets		1.10	%(e)		1.28	%(e)
Portfolio turnover rate		50	%(d)		71	%(d)
Net assets, end of period (in thousands)	$	15,598		$	13,025
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		0.72	%(e)		0.67	%(e)
Net investment income (loss) to average net assets		1.07	%(e)		1.28	%(e)

*	Class K commenced operations on December 30, 2019.
(a)	The per share data presented above is based on the average shares outstanding for the period presented.
(b)	Amount is less than $0.01.
(c)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period.
(d)	Not annualized.
(e)	Annualized.

The accompanying notes are an integral part of these financial statements.

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Financial Highlights (continued)

	Six Months										,
	Ended			Year			Year			Year			Year			Year
	6/30/20			Ended			Ended			Ended			Ended			Ended
	(unaudited)			12/31/19			12/31/18			12/31/17			12/31/16*			12/31/15*
Class R
Net asset value, beginning of period	$	29.74		$	24.89		$	28.93		$	29.01		$	32.04		$	36.80
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.04		$	0.13		$	0.17		$	0.17		$	0.21		$	0.19
Net realized and unrealized gain (loss) on investments		(0.12	)		7.37			(0.53	)		5.76			2.57			(0.42	)
Net increase (decrease) from investment operations	$	(0.08	)	$	7.50		$	(0.36	)	$	5.93		$	2.78		$	(0.23	)
Distributions to shareowners:
Net investment income	$	(0.04	)	$	(0.12	)	$	(0.16	)	$	(0.15	)	$	(0.22	)	$	(0.19	)
Net realized gain		—			(2.53	)		(3.52	)		(5.86	)		(5.59	)		(4.34	)
Total distributions	$	(0.04	)	$	(2.65	)	$	(3.68	)	$	(6.01	)	$	(5.81	)	$	(4.53	)
Net increase (decrease) in net asset value	$	(0.12	)	$	4.85		$	(4.04	)	$	(0.08	)	$	(3.03	)	$	(4.76	)
Net asset value, end of period	$	29.62		$	29.74		$	24.89		$	28.93		$	29.01		$	32.04
Total return (b)		(0.24	)%(c)		30.45	%		(2.12	)%		20.99	%		9.12	%		(0.77	)%(d)
Ratio of net expenses to average net assets		1.49	%(e)		1.45	%		1.37	%		1.38	%		1.41	%		1.30	%
Ratio of net investment income (loss) to average net assets		0.28	%(e)		0.44	%		0.57	%		0.55	%		0.66	%		0.54	%
Portfolio turnover rate		50	%(c)		71	%		60	%		58	%		62	%		50	%
Net assets, end of period (in thousands)	$	43,561		$	48,363		$	44,314		$	51,716		$	52,795		$	56,380
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		1.52	%(e)		1.45	%		1.37	%		1.38	%		1.41	%		1.30	%
Net investment income (loss) to average net assets		0.25	%(e)		0.44	%		0.57	%		0.55	%		0.66	%		0.54	%

*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per share data presented above is based on the average shares outstanding for the period presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period.
(c)	Not annualized.
(d)	If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.80)%.
(e)	Annualized.

The accompanying notes are an integral part of these financial statements.

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	Six Months
	Ended			Year			Year			Year			Year			Year
	6/30/20			Ended			Ended			Ended			Ended			Ended
	(unaudited)			12/31/19			12/31/18			12/31/17			12/31/16*			12/31/15*
Class Y
Net asset value, beginning of period	$	30.04		$	25.11		$	29.17		$	29.19		$	32.18		$	36.94
Increase (decrease) from investment operations:
Net investment income (loss) (a)	$	0.15		$	0.32		$	0.35		$	0.39		$	0.43		$	0.42
Net realized and unrealized gain (loss) on investments		(0.13	)		7.45			(0.55	)		5.81			2.59			(0.43	)
Net increase (decrease) from investment operations	$	0.02		$	7.77		$	(0.20	)	$	6.20		$	3.02		$	(0.01	)
Distributions to shareowners:
Net investment income	$	(0.14	)	$	(0.31	)	$	(0.34	)	$	(0.36	)	$	(0.42	)	$	(0.41	)
Net realized gain		—			(2.53	)		(3.52	)		(5.86	)		(5.59	)		(4.34	)
Total distributions	$	(0.14	)	$	(2.84	)	$	(3.86	)	$	(6.22	)	$	(6.01	)	$	(4.75	)
Net increase (decrease) in net asset value	$	(0.12	)	$	4.93		$	(4.06	)	$	(0.02	)	$	(2.99	)	$	(4.76	)
Net asset value, end of period	$	29.92		$	30.04		$	25.11		$	29.17		$	29.19		$	32.18
Total return (b)		0.14	%(c)		31.31	%		(1.56	)%		21.85	%		9.86	%		(0.14	)%(d)
Ratio of net expenses to average net assets		0.73	%(e)		0.81	%		0.77	%		0.69	%		0.73	%		0.68	%
Ratio of net investment income (loss) to average net assets		1.06	%(e)		1.09	%		1.17	%		1.24	%		1.34	%		1.14	%
Portfolio turnover rate		50	%(c)		71	%		60	%		58	%		62	%		50	%
Net assets, end of period (in thousands)	$	138,891		$	107,783		$	95,481		$	108,729		$	110,080		$	153,661
Ratios with no waiver of fees and assumption of expenses by
the Adviser and no reduction for fees paid indirectly:
Total expenses to average net assets		0.83	%(e)		0.81	%		0.77	%		0.69	%		0.73	%		0.68	%
Net investment income (loss) to average net assets		0.96	%(e)		1.09	%		1.17	%		1.24	%		1.34	%		1.14	%

*	The Fund was audited by an independent registered public accounting firm other than Ernst & Young LLP.
(a)	The per share data presented above is based on the average shares outstanding for the period presented.
(b)	Assumes initial investment at net asset value at the beginning of each period, reinvestment of all distributions and the complete redemption of the investment at net asset value at the end of each period.
(c)	Not annualized.
(d)	If the Fund had not recognized gains in settlement of class action lawsuits during the year ended December 31, 2015, the total return would have been (0.17)%.
(e)	Annualized.

The accompanying notes are an integral part of these financial statements.

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Notes to Financial Statements | 6/30/20 (unaudited)

1. Organization and Significant Accounting Policies

Pioneer Fund (the “Fund”) is a Delaware statutory trust. The Fund is registered under the Investment Company Act of 1940 as a diversified, open-end management investment company. The investment objective of the Fund is to provide reasonable income and capital growth.

The Fund offers five classes of shares designated as Class A, Class C, Class K, Class R and Class Y shares. Class K commenced operations on December 30, 2019. Each class of shares represents an interest in the same portfolio of investments of the Fund and has identical rights (based on relative net asset values) to assets and liquidation proceeds. Share classes can bear different rates of class-specific fees and expenses, such as transfer agent and distribution fees. Differences in class-specific fees and expenses will result in differences in net investment income and, therefore, the payment of different dividends from net investment income earned by each class. The Amended and Restated Declaration of Trust of the Fund gives the Board of Trustees the flexibility to specify either per-share voting or dollar-weighted voting when submitting matters for shareowner approval. Under per-share voting, each share of a class of the Fund is entitled to one vote. Under dollar-weighted voting, a shareowner’s voting power is determined not by the number of shares owned, but by the dollar value of the shares on the record date. Each share class has exclusive voting rights with respect to matters affecting only that class, including with respect to the distribution plan for that class. There is no distribution plan for Class K and Class Y shares.

Amundi Pioneer Asset Management, Inc., an indirect, wholly owned subsidiary of Amundi and Amundi’s wholly owned subsidiary, Amundi USA, Inc., serves as the Fund’s investment adviser (the “Adviser”). Amundi Pioneer Distributor, Inc., an affiliate of Amundi Pioneer Asset Management, Inc., serves as the Fund’s distributor (the “Distributor”).

In August 2018, the Securities and Exchange Commission (“SEC”) released a Disclosure Update and Simplification Final Rule. The Final Rule amends Regulation S-X disclosures requirements to conform them to U.S. Generally Accepted Accounting Principles (“U.S. GAAP”) for investment companies. The Fund’s financial statements were prepared in compliance with the new amendments to Regulation S-X.

The Fund is an investment company and follows investment company accounting and reporting guidance under U.S. GAAP. U.S. GAAP requires the management of the Fund to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets

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and liabilities at the date of the financial statements, and the reported amounts of income, expenses and gain or loss on investments during the reporting period. Actual results could differ from those estimates.

The following is a summary of significant accounting policies followed by the Fund in the preparation of its financial statements:

A. Security Valuation

The net asset value of the Fund is computed once daily, on each day the New York Stock Exchange (“NYSE”) is open, as of the close of regular trading on the NYSE.

Equity securities that have traded on an exchange are valued by using the last sale price on the principal exchange where they are traded. Equity securities that have not traded on the date of valuation, or securities for which sale prices are not available, generally are valued using the mean between the last bid and asked prices or, if both last bid and asked prices are not available, at the last quoted bid price. Last sale and bid and asked prices are provided by independent third party pricing services. In the case of equity securities not traded on an exchange, prices are typically determined by independent third party pricing services using a variety of techniques and methods.

The value of foreign securities is translated into U.S. dollars based on foreign currency exchange rate quotations supplied by a third party pricing source. Trading in non-U.S. equity securities is substantially completed each day at various times prior to the close of the NYSE. The values of such securities used in computing the net asset value of the Fund’s shares are determined as of such times. The Fund may use a fair value model developed by an independent pricing service to value non-U.S. equity securities.

Fixed-income securities are valued by using prices supplied by independent pricing services, which consider such factors as market prices, market events, quotations from one or more brokers, Treasury spreads, yields, maturities and ratings, or may use a pricing matrix or other fair value methods or techniques to provide an estimated value of the security or instrument. A pricing matrix is a means of valuing a debt security on the basis of current market prices for other debt securities, historical trading patterns in the market for fixed income securities and/or other factors. Non-U.S. debt securities that are listed on an exchange will be valued at the bid price obtained from an independent third party pricing service. When independent third party pricing services are unable to supply prices, or when prices or market quotations are considered to be unreliable, the value of that security may be determined sing quotations from one or more broker-dealers.

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Repurchase agreements are valued at par. Cash may include overnight time deposits at approved financial institutions.

Securities for which independent pricing services or broker-dealers are unable to supply prices or for which market prices and/or quotations are not readily available or are considered to be unreliable are valued by a fair valuation team comprised of certain personnel of the Adviser pursuant to procedures adopted by the Fund’s Board of Trustees. The Adviser’s fair valuation team uses fair value methods approved by the Valuation Committee of the Board of Trustees. The Adviser’s fair valuation team is responsible for monitoring developments that may impact fair valued securities and for discussing and assessing fair values on an ongoing basis, and at least quarterly, with the Valuation Committee of the Board of Trustees.

Inputs used when applying fair value methods to value a security may include credit ratings, the financial condition of the company, current market conditions and comparable securities. The Fund may use fair value methods if it is determined that a significant event has occurred after the close of the exchange or market on which the security trades and prior to the determination of the Fund’s net asset value. Examples of a significant event might include political or economic news, corporate restructurings, natural disasters, terrorist activity or trading halts. Thus, the valuation of the Fund’s securities may differ significantly from exchange prices, and such differences could be material.

At June 30, 2020, no securities were valued using fair value methods (other than securities valued using prices supplied by independent pricing services, broker-dealers or using a third party insurance industry pricing model).

B. Investment Income and Transactions

Dividend income is recorded on the ex-dividend date, except that certain dividends from foreign securities where the ex-dividend date may have passed are recorded as soon as the Fund becomes aware of the ex-dividend data in the exercise of reasonable diligence.

Interest income, including interest on income-bearing cash accounts, is recorded on the accrual basis. Dividend and interest income are reported net of unrecoverable foreign taxes withheld at the applicable country rates and net of income accrued on defaulted securities.

Interest and dividend income payable by delivery of additional shares is reclassified as PIK (payment-in-kind) income upon receipt and is included in interest and dividend income, respectively.

Security transactions are recorded as of trade date. Gains and losses on sales of investments are calculated on the identified cost method for both financial reporting and federal income tax purposes.

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C. Foreign Currency Translation

The books and records of the Fund are maintained in U.S. dollars. Amounts denominated in foreign currencies are translated into U.S. dollars using current exchange rates.

Net realized gains and losses on foreign currency transactions, if any, represent, among other things, the net realized gains and losses on foreign currency exchange contracts, disposition of foreign currencies and the difference between the amount of income accrued and the U.S. dollars actually received. Further, the effects of changes in foreign currency exchange rates on investments are not segregated on the Statement of Operations from the effects of changes in the market prices of those securities, but are included with the net realized and unrealized gain or loss on investments.

D. Federal Income Taxes

It is the Fund’s policy to comply with the requirements of the Internal Revenue Code applicable to regulated investment companies and to distribute all of its net taxable income and net realized capital gains, if any, to its shareowners. Therefore, no provision for federal income taxes is required. As of December 31, 2019, the Fund did not accrue any interest or penalties with respect to uncertain tax positions, which, if applicable, would be recorded as an income tax expense on the Statement of Operations. Tax returns filed within the prior three years remain subject to examination by federal and state tax authorities.

The amount and character of income and capital gain distributions to shareowners are determined in accordance with federal income tax rules, which may differ from U.S. GAAP. Distributions in excess of net investment income or net realized gains are temporary over distributions for financial statement purposes resulting from differences in the recognition or classification of income or distributions for financial statement and tax purposes. Capital accounts within the financial statements are adjusted for permanent book/tax differences to reflect tax character, but are not adjusted for temporary differences.

The tax character of current year distributions payable will be determined at the end of the current taxable year. The tax character of distributions paid during the year ended December 31, 2019 was as follows:

	2019
Distributions paid from:
Ordinary income	$	73,075,505
Long-term capital gain		394,220,054
Total	$	467,295,559

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The following shows the components of distributable earnings on a federal income tax basis at December 31, 2019:

	2019
Distributable earnings:
Undistributed ordinary income	$	20,847,082
Undistributed long-term capital gain		37,398,975
Net unrealized appreciation		1,364,511,072
Total	$	1,422,757,129

The difference between book-basis and tax-basis net unrealized appreciation is attributable to the tax deferral of losses on wash sales and on the tax-basis adjustment on common stocks.

E. Fund Shares

The Fund records sales and repurchases of its shares as of trade date. The Distributor earned $187,058 in underwriting commissions on the sale of Class A shares during the six months ended June 30, 2020.

F. Class Allocations

Income, common expenses and realized and unrealized gains and losses are calculated at the Fund level and allocated daily to each class of shares based on its respective percentage of adjusted net assets at the beginning of the day.

Distribution fees are calculated based on the average daily net asset value attributable to Class A, Class C and Class R shares of the Fund, respectively (see Note 4). Class K and Class Y shares do not pay distribution fees. All expenses and fees paid to the Fund’s transfer agent for its services are allocated among the classes of shares based on the number of accounts in each class and the ratable allocation of related out-of-pocket expenses (see Note 3).

Distributions to shareowners are recorded as of the ex-dividend date. Distributions paid by the Fund with respect to each class of shares are calculated in the same manner and at the same time, except that net investment income dividends to Class A, Class C, Class K, Class R and Class Y shares can reflect different transfer agent and distribution expense rates.

G. Repurchase Agreements

Repurchase agreements are arrangements under which the Fund purchases securities from a broker-dealer or a bank, called the counterparty, upon the agreement of the counterparty to repurchase the securities from the Fund at a later date, and at a specific price, which is typically higher than the purchase price paid by the Fund. The securities purchased serve as the Fund’s collateral for the obligation of the counterparty to repurchase the securities. The value of the collateral, including accrued interest, is required to be equal to or in excess

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of the repurchase price. The collateral for all repurchase agreements is held in safekeeping in the customer-only account of the Fund’s custodian or a sub-custodian of the Fund. The Adviser is responsible for determining that the value of the collateral remains at least equal to the repurchase price. In the event of a default by the counterparty, the Fund is entitled to sell the securities, but the Fund may not be able to sell them for the price at which they were purchased, thus causing a loss to the Fund. Additionally, if the counterparty becomes insolvent, there is some risk that the Fund will not have a right to the securities, or the immediate right to sell the securities. As of and for the year ended December 31, 2019, the Fund had no open repurchase agreements.

H. Risks

The value of securities held by the Fund may go up or down, sometimes rapidly or unpredictably, due to general market conditions, such as real or perceived adverse economic, political or regulatory conditions, recessions, the spread of infectious illness or other public health issues, inflation, changes in interest rates, lack of liquidity in the bond markets or adverse investor sentiment. In the past several years, financial markets have experienced increased volatility, depressed valuations, decreased liquidity and heightened uncertainty. These conditions may continue, recur, worsen or spread. A general rise in interest rates could adversely affect the price and liquidity of fixed-income securities and could also result in increased redemptions from the Fund.

At times, the Fund’s investments may represent industries or industry sectors that are interrelated or have common risks, making the Fund more susceptible to any economic, political, or regulatory developments or other risks affecting those industries and sectors. The Fund’s investments in foreign markets and countries with limited developing markets may subject the Fund to a greater degree of risk than investments in a developed market. These risks include disruptive political or economic conditions and the imposition of adverse governmental laws or currency exchange restrictions.

With the increased use of technologies such as the Internet to conduct business, the Fund is susceptible to operational, information security and related risks. While the Fund’s Adviser has established business continuity plans in the event of, and risk management systems to prevent, limit or mitigate, such cyber-attacks, there are inherent limitations in such plans and systems, including the possibility that certain risks have not been identified. Furthermore, the Fund cannot control the cybersecurity plans and systems put in place by service providers to the Fund such as Brown Brothers Harriman & Co., the Fund’s custodian and accounting agent, and DST Asset Manager Solutions, Inc., the Fund’s transfer agent. In addition, many

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beneficial owners of Fund shares hold them through accounts at broker-dealers, retirement platforms and other financial market participants over which neither the Fund nor Amundi Pioneer exercises control. Each of these may in turn rely on service providers to them, which are also subject to the risk of cyber-attacks. Cybersecurity failures or breaches at Amundi Pioneer or the Fund’s service providers or intermediaries have the ability to cause disruptions and impact business operations, potentially resulting in financial losses, interference with the Fund’s ability to calculate its net asset value, impediments to trading, the inability of Fund shareowners to effect share purchases, redemptions or exchanges or receive distributions, loss of or unauthorized access to private shareowner information and violations of applicable privacy and other laws, regulatory fines, penalties, reputational damage, or additional compliance costs. Such costs and losses may not be covered under any insurance. In addition, maintaining vigilance against cyber-attacks may involve substantial costs over time, and system enhancements may themselves be subject to cyber-attacks.

COVID-19

The respiratory illness COVID-19 caused by a novel coronavirus has resulted in a global pandemic and major disruption to economies and markets around the world, including the United States. Global financial markets have experienced extreme volatility and severe losses, and trading in many instruments has been disrupted. Liquidity for many instruments has been greatly reduced for periods of time. Some interest rates are very low and in some cases yields are negative. Some sectors of the economy and individual issuers have experienced particularly large losses. These circumstances may continue for an extended period of time, and may continue to affect adversely the value and liquidity of the Fund’s investments. The ultimate economic fallout from the pandemic, and the long-term impact on economies, markets, industries and individual issuers, are not known. Governments and central banks, including the Federal Reserve in the U.S., have taken extraordinary and unprecedented actions to support local and global economies and the financial markets. These actions have resulted in significant expansion of public debt, including in the U.S. The impact of these measures, and whether they will be effective to mitigate the economic and market disruption, will not be known for some time. The consequences of high public debt, including its future impact on the economy and securities markets, likewise may not be known for some time.

The Fund’s prospectus contains unaudited information regarding the Fund’s principal risks. Please refer to that document when considering the Fund’s principal risks.

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2. Management Agreement

The Adviser manages the Fund’s portfolio. Management fees are calculated daily and paid monthly at the annual rate of 0.60% of the Fund’s average daily net assets up to $7.5 billion, 0.575% on the next $2.5 billion of the Fund’s average daily net assets and 0.55% on the excess over $10 billion of the Fund’s average daily net assets. The basic fee can increase or decrease by a maximum of 0.10% based on the investment performance of the Fund’s Class A shares as compared to the Standard and Poor’s 500 Index. The performance comparison is made for a rolling 36-month period. In addition, the Adviser, contractually limits any positive adjustment of the Fund’s management fee to 0.10% of the Fund’s average daily net assets on an annual basis (i.e., to a maximum annual fee of 0.70% after the performance adjustment). For the six months ended June 30, 2020, the performance comparison did not result in an adjustment to the basic fee. For the six months ended June 30, 2020, the net management fee (excluding waivers and/or assumption of expenses) was equivalent to 0.66% (annualized) of the Fund’s average daily net assets.

Effective February 28, 2020, the Adviser has contractually agreed to limit ordinary operating expenses (ordinary operating expenses means all fund expenses other than extraordinary expenses, such as litigation, taxes, brokerage commissions and acquired fund fees and expenses) of the Fund to the extent required to reduce Fund expenses to 0.70% of the average daily net assets attributable Class Y shares. These expense limitations are in effect through May 1, 2021. Fees waived and expenses reimbursed during the six months ended June 30, 2020 are reflected on the Statement of Operations.

In addition, under the management and administration agreements, certain other services and costs, including accounting, regulatory reporting and insurance premiums, are paid by the Fund as administrative reimbursements. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $604,936 in management fees, administrative costs and certain other reimbursements payable to the Adviser at June 30, 2020.

3. Transfer Agent

DST Asset Manager Solutions, Inc. serves as the transfer agent to the Fund at negotiated rates. Transfer agent fees and payables shown on the Statement of Operations and the Statement of Assets and Liabilities, respectively, include sub-transfer agent expenses incurred through the Fund’s omnibus relationship contracts.

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In addition, the Fund reimbursed the transfer agent for out-of-pocket expenses incurred by the transfer agent related to shareowner communications activities such as proxy and statement mailings, and outgoing phone calls. For the six months ended June 30, 2020, such out-of-pocket expenses by class of shares were as follows:

Shareowner Communications:
Class A	$	1,017,008
Class C		6,281
Class R		1,290
Class Y		3,068
Total	$	1,027,647

4. Distribution and Service Plans

The Fund has adopted a distribution plan (the “Plan”) pursuant to Rule 12b-1 of the Investment Company Act of 1940 with respect to its Class A, Class C and Class R shares. Pursuant to the Plan, the Fund pays the Distributor 0.25% of the average daily net assets attributable to Class A shares as compensation for personal services and/or account maintenance services or distribution services with regard to Class A shares. Pursuant to the Plan, the Fund also pays the Distributor 1.00% of the average daily net assets attributable to Class C shares. The fee for Class C shares consists of a 0.25% service fee and a 0.75% distribution fee paid as compensation for personal services and/or account maintenance services or distribution services with regard to Class C shares. Pursuant to the Plan, the Fund further pays the Distributor 0.50% of the average daily net assets attributable to Class R shares for distribution services. Included in “Due to affiliates” reflected on the Statement of Assets and Liabilities is $230,701 in distribution fees payable to the Distributor at June 30, 2020.

The Fund also has adopted a separate service plan for Class R shares (the “Service Plan”). The Service Plan authorizes the Fund to pay securities dealers, plan administrators or other service organizations that agree to provide certain services to retirement plans or plan participants holding shares of the Fund a service fee of up to 0.25% of the Fund’s average daily net assets attributable to Class R shares held by such plans.

In addition, redemptions of Class A and Class C shares may be subject to a contingent deferred sales charge (“CDSC”). A CDSC of 1.00% may be imposed on redemptions of certain net asset value purchases of Class A shares within 12 months of purchase. Redemptions of Class C shares within 12 months of purchase are subject to a CDSC of 1.00%, based on the lower of cost or market value of shares being redeemed. Shares purchased as part of an exchange remain subject to any CDSC that applied to the original purchase of those

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shares. There is no CDSC for Class K, Class R or Class Y shares. Proceeds from the CDSCs are paid to the Distributor. For the six months ended June 30, 2020, CDSCs in the amount of $9,494 were paid to the Distributor.

5. Line of Credit Facility

The Fund, along with certain other funds in the Pioneer Family of Funds (the “Funds”), participates in a committed, unsecured revolving line of credit facility. Borrowings are used solely for temporary or emergency purposes. The Fund may borrow up to the lesser of the amount available under the credit facility or the limits set for borrowing by the Fund’s prospectus and the 1940 Act. Effective March 11, 2020, the Fund participates in a facility in the amount of $300 million. Prior to March 11, 2020, the Fund participated in a facility in the amount of $250 million. Under such facility, depending on the type of loan, interest on borrowings is payable at the London Interbank Offered Rate (“LIBOR”) plus a credit spread. The Fund also pays an annual commitment fee to participate in a credit facility. The commitment fee is allocated among participating Funds based on an allocation schedule set forth in the credit agreement. For the six months ended June 30, 2020, the Fund had no borrowings under the credit facility.

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Statement Regarding Liquidity Risk Management Program

As required by law, the Fund has adopted and implemented a liquidity risk management program (the “Program”) that is designed to assess and manage liquidity risk. Liquidity risk is the risk that the Fund could not meet requests to redeem its shares without significant dilution of remaining investors’ interests in the Fund. The Fund’s Board of Trustees designated a liquidity risk management committee (the “Committee”) consisting of employees of Amundi Pioneer Asset Management, Inc. (the “Adviser”) to administer the Program.

The Committee provided the Board of Trustees with a report that addressed the operation of the Program and assessed its adequacy and effectiveness of implementation (the “Report”). The Report covered the period from December 1, 2018 through March 31, 2020 (the “Reporting Period”).

The Report confirmed that, throughout the Reporting Period, the Committee had monitored the Fund’s portfolio liquidity and liquidity risk on an ongoing basis, as described in the Program and in Board reporting throughout the Reporting Period.

The Report discussed the Committee’s annual review of the Program, which addressed, among other things, the following elements of the Program:

The Committee reviewed the Fund’s investment strategy and liquidity of portfolio investments during both normal and reasonably foreseeable stressed conditions. The Committee noted that the Fund’s investment strategy continues to be appropriate for an open-end fund, taking into account, among other things, whether and to what extent the Fund held less liquid and illiquid assets and the extent to which any such investments affected the Fund’s ability to meet redemption requests. In managing and reviewing the Fund’s liquidity risk, the Committee also considered the extent to which the Fund’s investment strategy involves a relatively concentrated portfolio or large positions in particular issuers, the extent to which the Fund uses borrowing for investment purposes, and the extent to which the Fund uses derivatives (including for hedging purposes). The Committee also reviewed the Fund’s short-term and long-term cash flow projections during both normal and reasonably foreseeable stressed conditions. In assessing the Fund’s cash flow projections, the Committee considered, among other factors, historical net redemption activity, redemption policies, ownership concentration, distribution channels, and the degree of certainty associated with the Fund’s short-term and long-term cash flow projections. The Committee also considered the Fund’s holdings of cash and cash equivalents, as well as borrowing arrangements and other funding sources, including, if applicable, the Fund’s participation in a credit

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facility, as components of the Fund’s ability to meet redemption requests. The Fund has adopted an in-kind redemption policy which may be utilized to meet larger redemption requests.

The Committee reviewed the Program’s liquidity classification methodology for categorizing the Fund’s investments into one of four liquidity buckets. In reviewing the Fund’s investments, the Committee considered, among other factors, whether trading varying portions of a position in a particular portfolio investment or asset class in sizes the Fund would reasonably anticipate trading, would be reasonably expected to significantly affect liquidity.

The Committee performed an analysis to determine whether the Fund is required to maintain a Highly Liquid Investment Minimum, and determined that no such minimum is required because the Fund primarily holds highly liquid investments.

The Report stated that the Committee concluded the Program operates adequately and effectively, in all material respects, to assess and manage the Fund’s liquidity risk throughout the Reporting Period.

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Trustees, Officers and Service Providers

Trustees	Officers
Thomas J. Perna, Chairman	Lisa M. Jones, President and
John E. Baumgardner, Jr.	Chief Executive Officer
Diane Durnin	Mark E. Bradley, Treasurer and
Benjamin M. Friedman	Chief Financial and
Lisa M. Jones	Accounting Officer
Lorraine H. Monchak	Christopher J. Kelley, Secretary and
Marguerite A. Piret	Chief Legal Officer
Fred J. Ricciardi
Kenneth J. Taubes

Investment Adviser and Administrator

Amundi Pioneer Asset Management, Inc.

Custodian and Sub-Administrator
Brown Brothers Harriman & Co.

Principal Underwriter
Amundi Pioneer Distributor, Inc.

Legal Counsel
Morgan, Lewis & Bockius LLP

Transfer Agent
DST Asset Manager Solutions, Inc.

Proxy Voting Policies and Procedures of the Fund are available without charge, upon request, by calling our toll free number (1-800-225-6292). Information regarding how the Fund voted proxies relating to portfolio securities during the most recent 12-month period ended June 30 is publicly available to shareowners at www.amundipioneer.com/us. This information is also available on the Securities and Exchange Commission’s web site at www.sec.gov.

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How to Contact Amundi Pioneer

We are pleased to offer a variety of convenient ways for you to contact us for assistance or information.

Call us for:
Account Information, including existing accounts,
new accounts, prospectuses, applications
and service forms		1-800-225-6292

FactFone^SMfor automated fund yields, prices,
account information and transactions		1-800-225-4321

Retirement plans information		1-800-622-0176

Write to us:
Amundi Pioneer
P.O. Box 219427
Kansas City, MO 64121-9427

Our toll-free fax		1-800-225-4240

Our internet e-mail address	us.askamundipioneer@amundipioneer.com
(for general questions about Amundi Pioneer only)


Visit our web site: www.amundipioneer.com/us

This report must be preceded or accompanied by a prospectus.

The Fund files a complete schedule of portfolio holdings with the Securities and Exchange Commission for the first and third quarters of each fiscal year as an exhibit to its reports on Form N-PORT. Shareholders may view the filed Form N-PORT by visiting the Commission’s web site at https://www.sec.gov.

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Amundi Pioneer Asset Management, Inc.

60 State Street

Boston, MA 02109

www.amundipioneer.com/us

Securities offered through Amundi Pioneer Funds Distributor, Inc.
60 State Street, Boston, MA 02109
Underwriter of Pioneer Mutual Funds, Member SIPC

ITEM 2. CODE OF ETHICS.

(a) Disclose whether, as of the end of the period covered by the report, the registrant has adopted a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party. If the registrant has not adopted such a code of ethics, explain why it has not done so.

The registrant has adopted, as of the end of the period covered by this report, a code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer and controller.

(b) For purposes of this Item, the term “code of ethics” means written standards that are reasonably designed to deter wrongdoing and to promote:

(1) Honest and ethical conduct, including the ethical handling of actual or apparent conflicts of interest between personal and professional relationships;

(2) Full, fair, accurate, timely, and understandable disclosure in reports and documents that a registrant files with, or submits to, the Commission and in other public communications made by the registrant;

(3) Compliance with applicable governmental laws, rules, and regulations;

(4) The prompt internal reporting of violations of the code to an appropriate person or persons identified in the code; and

(5) Accountability for adherence to the code.

(c) The registrant must briefly describe the nature of any amendment, during the period covered by the report, to a provision of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item. The registrant must file a copy of any such amendment as an exhibit pursuant to Item 10(a), unless the registrant has elected to satisfy paragraph (f) of this Item by posting its code of ethics on its website pursuant to paragraph (f)(2) of this Item, or by undertaking to provide its code of ethics to any person without charge, upon request, pursuant to paragraph (f)(3) of this Item.

The registrant has made no amendments to the code of ethics during the period covered by this report.

(d) If the registrant has, during the period covered by the report, granted a waiver, including an implicit waiver, from a provision of the code of ethics to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, regardless of whether these individuals are employed by the registrant or a third party, that relates to one or more of the items set forth in paragraph (b) of this Item, the registrant must briefly describe the nature of the waiver, the name of the person to whom the waiver was granted, and the date of the waiver.

Not applicable.

(e) If the registrant intends to satisfy the disclosure requirement under paragraph (c) or (d) of this Item regarding an amendment to, or a waiver from, a provision of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions and that relates to any element of the code of ethics definition enumerated in paragraph (b) of this Item by posting such information on its Internet website, disclose the registrant’s Internet address and such intention.

Not applicable.

(f) The registrant must:

(1) File with the Commission, pursuant to Item 12(a)(1), a copy of its code of ethics that applies to the registrant’s principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions, as an exhibit to its annual report on this Form N-CSR (see attachment);

(2) Post the text of such code of ethics on its Internet website and disclose, in its most recent report on this Form N-CSR, its Internet address and the fact that it has posted such code of ethics on its Internet website; or

(3) Undertake in its most recent report on this Form N-CSR to provide to any person without charge, upon request, a copy of such code of ethics and explain the manner in which such request may be made. See Item 10(2)

ITEM 3. AUDIT COMMITTEE FINANCIAL EXPERT.

(a) (1) Disclose that the registrant’s board of trustees has determined that the registrant either:

(i) Has at least one audit committee financial expert serving on its audit committee; or

(ii) Does not have an audit committee financial expert serving on its audit committee.

The registrant’s Board of Trustees has determined that the registrant has at least one audit committee financial expert.

(2) If the registrant provides the disclosure required by paragraph (a)(1)(i) of this Item, it must disclose the name of the audit committee financial expert and whether that person is “independent.” In order to be considered “independent” for purposes of this Item, a member of an audit committee may not, other than in his or her capacity as a member of the audit committee, the board of trustees, or any other board committee:

(i) Accept directly or indirectly any consulting, advisory, or other compensatory fee from the issuer; or

(ii) Be an “interested person” of the investment company as defined in Section 2(a)(19) of the Act (15 U.S.C. 80a-2(a)(19)).

Mr. Fred J. Ricciardi, an independent trustee, is such an audit committee financial expert.

(3) If the registrant provides the disclosure required by paragraph (a)(1) (ii) of this Item, it must explain why it does not have an audit committee financial expert.

Not applicable.

ITEM 4. PRINCIPAL ACCOUNTANT FEES AND SERVICES.

(a) Disclose, under the caption AUDIT FEES, the aggregate fees billed for each of the last two fiscal years for professional services rendered by the principal accountant for the audit of the registrant’s annual financial statements or services that are normally provided by the accountant in connection with statutory and regulatory filings or engagements for those fiscal years.

N/A

(b) Disclose, under the caption AUDIT-RELATED FEES, the aggregate fees billed in each of the last two fiscal years for assurance and related services by the principal accountant that are reasonably related to the performance of the audit of the registrant’s financial statements and are not reported under paragraph (a) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

N/A

(c) Disclose, under the caption TAX FEES, the aggregate fees billed in each of the last two fiscal years for professional services rendered by the principal accountant for tax compliance, tax advice, and tax planning. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

N/A

(d) Disclose, under the caption ALL OTHER FEES, the aggregate fees billed in each of the last two fiscal years for products and services provided by the principal accountant, other than the services reported in paragraphs (a) through (c) of this Item. Registrants shall describe the nature of the services comprising the fees disclosed under this category.

N/A

(e) (1) Disclose the audit committee’s pre-approval policies and procedures described in paragraph (c)(7) of Rule 2-01 of Regulation S-X.

PIONEER FUNDS

APPROVAL OF AUDIT, AUDIT-RELATED, TAX AND OTHER SERVICES

PROVIDED BY THE INDEPENDENT AUDITOR

SECTION I - POLICY PURPOSE AND APPLICABILITY

The Pioneer Funds recognize the importance of maintaining the independence of their outside auditors. Maintaining independence is a shared responsibility involving Amundi Pioneer Asset Management, Inc, the audit committee and the independent auditors.

The Funds recognize that a Fund’s independent auditors: 1) possess knowledge of the Funds, 2) are able to incorporate certain services into the scope of the audit, thereby avoiding redundant work, cost and disruption of Fund personnel and processes, and 3) have expertise that has value to the Funds. As a result, there are situations where it is desirable to use the Fund’s independent auditors for services in addition to the annual audit and where the potential for conflicts of interests are minimal. Consequently, this policy, which is intended to comply with Rule 210.2-01(C)(7), sets forth guidelines and procedures to be followed by the Funds when retaining the independent audit firm to perform audit, audit-related tax and other services under those circumstances, while also maintaining independence.

Approval of a service in accordance with this policy for a Fund shall also constitute approval for any other Fund whose pre-approval is required pursuant to Rule 210.2-01(c)(7)(ii).

In addition to the procedures set forth in this policy, any non-audit services that may be provided consistently with Rule 210.2-01 may be approved by the Audit Committee itself and any pre-approval that may be waived in accordance with Rule 210.2-01(c)(7)(i)(C) is hereby waived.

Selection of a Fund’s independent auditors and their compensation shall be determined by the Audit Committee and shall not be subject to this policy.


SECTION II - POLICY

SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION		SPECIFIC PRE-APPROVED SERVICE SUBCATEGORIES

I. AUDIT SERVICES	Services that are directly		o Accounting research assistance
	related to performing the		o SEC consultation, registration
	independent audit of the Funds		statements, and reporting
			o Tax accrual related matters
			o Implementation of new accounting standards
			o Compliance letters (e.g. rating agency letters)
			o Regulatory reviews and assistance
			regarding financial matters
			o Semi-annual reviews (if requested)
			o Comfort letters for closed end offerings
II. AUDIT-RELATED	Services which are not		o AICPA attest and agreed-upon procedures
SERVICES	prohibited under Rule		o Technology control assessments
	210.2-01(C)(4) (the “Rule”)		o Financial reporting control assessments
	and are related extensions of		o Enterprise security architecture
	the audit services support the		assessment
	audit, or use the knowledge/expertise
	gained from the audit procedures as a
	foundation to complete the project.
	In most cases, if the Audit-Related
	Services are not performed by the
	Audit firm, the scope of the Audit
	Services would likely increase.
	The Services are typically well-defined
	and governed by accounting
	professional standards (AICPA,
	SEC, etc.)

AUDIT COMMITTEE APPROVAL POLICY		AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval		o A summary of all such
for the audit period for all		services and related fees
pre-approved specific service		reported at each regularly
subcategories. Approval of the		scheduled Audit Committee
independent auditors as		meeting.
auditors for a Fund shall
constitute pre approval for
these services.

o “One-time” pre-approval		o A summary of all such
for the fund fiscal year within		services and related fees
a specified dollar limit		(including comparison to
for all pre-approved		specified dollar limits)
specific service subcategories		reported quarterly.

o Specific approval is
needed to exceed the
pre-approved dollar limit for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for Audit-Related
Services not denoted as
“pre-approved”, or
to add a specific service
subcategory as “pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PRE-APPROVED SERVICE
		SUBCATEGORIES
III. TAX SERVICES	Services which are not	o Tax planning and support
	prohibited by the Rule,	o Tax controversy assistance
	if an officer of the Fund	o Tax compliance, tax returns, excise
	determines that using the	tax returns and support
	Fund’s auditor to provide	o Tax opinions
	these services creates
	significant synergy in
	the form of efficiency,
	minimized disruption, or
	the ability to maintain a
	desired level of
	confidentiality.


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval	o A summary of
for the fund fiscal year	all such services and
within a specified dollar limit	related fees
	(including comparison
	to specified dollar
	limits) reported
	quarterly.

o Specific approval is
needed to exceed the
pre-approved dollar limits for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for tax services not
denoted as pre-approved, or to
add a specific service subcategory as
“pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PRE-APPROVED SERVICE
		SUBCATEGORIES
IV. OTHER SERVICES	Services which are not	o Business Risk Management support
	prohibited by the Rule,	o Other control and regulatory
A. SYNERGISTIC,	if an officer of the Fund	compliance projects
UNIQUE QUALIFICATIONS	determines that using the
	Fund’s auditor to provide
	these services creates
	significant synergy in
	the form of efficiency,
	minimized disruption,
	the ability to maintain a
	desired level of
	confidentiality, or where
	the Fund’s auditors
	posses unique or superior
	qualifications to provide
	these services, resulting
	in superior value and
	results for the Fund.


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o “One-time” pre-approval	o A summary of
for the fund fiscal year within	all such services and
a specified dollar limit	related fees
	(including comparison
	to specified dollar
	limits) reported
	quarterly.
o Specific approval is
needed to exceed the
pre-approved dollar limits for
these services (see general
Audit Committee approval policy
below for details on obtaining
specific approvals)

o Specific approval is
needed to use the Fund’s
auditors for “Synergistic” or
“Unique Qualifications” Other
Services not denoted as
pre-approved to the left, or to
add a specific service
subcategory as “pre-approved”

SECTION III - POLICY DETAIL, CONTINUED


SERVICE CATEGORY	SERVICE CATEGORY DESCRIPTION	SPECIFIC PROHIBITED SERVICE
		SUBCATEGORIES
PROHIBITED SERVICES	Services which result	1. Bookkeeping or other services
	in the auditors losing	related to the accounting records or
	independence status	financial statements of the audit
	under the Rule.	client*
		2. Financial information systems design
		and implementation*
		3. Appraisal or valuation services,
		fairness* opinions, or
		contribution-in-kind reports
		4. Actuarial services (i.e., setting
		actuarial reserves versus actuarial
		audit work)*
		5. Internal audit outsourcing services*
		6. Management functions or human
		resources
		7. Broker or dealer, investment
		advisor, or investment banking services
		8. Legal services and expert services
		unrelated to the audit
		9. Any other service that the Public
		Company Accounting Oversight Board
		determines, by regulation, is
		impermissible


AUDIT COMMITTEE APPROVAL POLICY	AUDIT COMMITTEE REPORTING POLICY
o These services are not to be	o A summary of all
performed with the exception of the(*)	services and related
services that may be permitted	fees reported at each
if they would not be subject to audit	regularly scheduled
procedures at the audit client (as	Audit Committee meeting
defined in rule 2-01(f)(4)) level	will serve as continual
the firm providing the service.	confirmation that has
	not provided any
	restricted services.

GENERAL AUDIT COMMITTEE APPROVAL POLICY:

o For all projects, the officers of the Funds and the Fund’s auditors will each make an assessment to determine that any proposed projects will not impair independence.

o Potential services will be classified into the four non-restricted service categories and the “Approval of Audit, Audit-Related, Tax and Other Services” Policy above will be applied. Any services outside the specific pre-approved service subcategories set forth above must be specifically approved by the Audit Committee.

o At least quarterly, the Audit Committee shall review a report summarizing the services by service category, including fees, provided by the Audit firm as set forth in the above policy.

(2) Disclose the percentage of services described in each of paragraphs (b) through (d) of this Item that were approved by the audit committee pursuant to paragraph (c)(7)(i)(C) of Rule 2-01 of Regulation S-X.

N/A

(f) If greater than 50 percent, disclose the percentage of hours expended on the principal accountants engagement to audit the registrant’s financial statements for the most recent fiscal year that were attributed to work performed by persons other than the principal accountant’s full-time, permanent employees.

N/A

(g) Disclose the aggregate non-audit fees billed by the registrants accountant for services rendered to the registrant, and rendered to the registrants investment adviser (not including any sub-adviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the adviser that provides ongoing services to the registrant for each of the last two fiscal years of the registrant.

N/A

(h) Disclose whether the registrants audit committee of the board of trustees has considered whether the provision of non-audit services that were rendered to the registrants investment adviser (not including any subadviser whose role is primarily portfolio management and is subcontracted with or overseen by another investment adviser), and any entity controlling, controlled by, or under common control with the investment adviser that provides ongoing services to the registrant that were not pre-approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

The Fund’s audit committee of the Board of Trustees has considered whether the provision of non-audit services that were rendered to the Affiliates (as defined) that were not pre- approved pursuant to paragraph (c)(7)(ii) of Rule 2-01 of Regulation S-X is compatible with maintaining the principal accountant’s independence.

ITEM 5. AUDIT COMMITTEE OF LISTED REGISTRANTS

(a) If the registrant is a listed issuer as defined in Rule 10A-3 under the Exchange Act (17 CFR 240.10A-3), state whether or not the registrant has a separately-designated standing audit committee established in accordance with Section 3(a)(58)(A) of the Exchange Act (15 U.S.C. 78c(a)(58)(A)). If the registrant has such a committee, however designated, identify each committee member. If the entire board of directors is acting as the registrant’s audit committee as specified in Section 3(a)(58)(B) of the Exchange Act (15 U.S.C. 78c(a)(58)(B)), so state.

N/A

(b) If applicable, provide the disclosure required by Rule 10A-3(d) under the Exchange Act (17 CFR 240.10A-3(d)) regarding an exemption from the listing standards for audit committees.

N/A

ITEM 6. SCHEDULE OF INVESTMENTS.

File Schedule of Investments in securities of unaffiliated issuers as of the close of the reporting period as set forth in 210.1212 of Regulation S-X [17 CFR 210.12-12], unless the schedule is included as part of the report to shareholders filed under Item 1 of this Form.

Included in Item 1

ITEM 7. DISCLOSURE OF PROXY VOTING POLICIES AND PROCEDURES FOR CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

A closed-end management investment company that is filing an annual report on this Form N-CSR must, unless it invests exclusively in non-voting securities, describe the policies and procedures that it uses to determine how to vote proxies relating to portfolio securities, including the procedures that the company uses when a vote presents a conflict between the interests of its shareholders, on the one hand, and those of the company’s investment adviser; principal underwriter; or any affiliated person (as defined in Section 2(a)(3) of the Investment Company Act of 1940 (15 U.S.C. 80a-2(a)(3)) and the rules thereunder) of the company, its investment adviser, or its principal underwriter, on the other. Include any policies and procedures of the company’s investment adviser, or any other third party, that the company uses, or that are used on the company’s behalf, to determine how to vote proxies relating to portfolio securities.

N/A

ITEM 8. PORTFOLIO MANAGERS OF CLOSED-END MANAGEMENT INVESTMENT COMPANIES.

(a) If the registrant is a closed-end management investment company that is filing an annual report on this Form N-CSR, provide the following information:

(1) State the name, title, and length of service of the person or persons employed by or associated with the registrant or an investment adviser of the registrant who are primarily responsible for the day-to-day management of the registrant’s portfolio (“Portfolio Manager”). Also state each Portfolio Manager’s business experience during the past 5 years.

N/A

ITEM 9. PURCHASES OF EQUITY SECURITIES BY CLOSED-END MANAGEMENT INVESTMENT COMPANY AND AFFILIATED PURCHASERS.

(a) If the registrant is a closed-end management investment company, in the following tabular format, provide the information specified in paragraph (b) of this Item with respect to any purchase made by or on behalf of the registrant or any affiliated purchaser, as defined in Rule 10b-18(a)(3) under the Exchange Act (17 CFR 240.10b-18(a)(3)), of shares or other units of any class of the registrant’s equity securities that is registered by the registrant pursuant to Section 12 of the Exchange Act (15 U.S.C. 781).

N/A

ITEM 10. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.

Describe any material changes to the procedures by which shareholders may recommend nominees to the registrant’s board of directors, where those changes were implemented after the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R(17 CFR 229.407)(as required by Item 22(b)(15)) of Schedule 14A (17 CFR 240.14a-101), or this Item.

There have been no material changes to the procedures by which the shareholders may recommend nominees to the registrant’s board of directors since the registrant last provided disclosure in response to the requirements of Item 407(c)(2)(iv) of Regulation S-R of Schedule 14(A) in its definitive proxy statement, or this item.

ITEM 11. CONTROLS AND PROCEDURES.

(a) Disclose the conclusions of the registrant’s principal executive and principal financials officers, or persons performing similar functions, regarding the effectiveness of the registrant’s disclosure controls and procedures (as defined in Rule 30a-3(c) under the Act (17 CFR 270.30a-3(c))) as of a date within 90 days of the filing date of the report that includes the disclosure required by this paragraph, based on the evaluation of these controls and procedures required by Rule 30a-3(b) under the Act (17 CFR 270.30(a)-3(b) and Rules 13a-15(b) or 15d-15(b) under the Exchange Act (17 CFR 240.13a-15(b) or 240.15d-15(b)).

The registrant’s principal executive officer and principal financial officer have concluded that the registrant’s disclosure controls and procedures are effective based on the evaluation of these controls and procedures as of a date within 90 days of the filing date of this report.

(b) Disclose any change in the registrant’s internal control over financial reporting (as defined in Rule 30a-3(d) under the Act (17CFR 270.30a-3(d)) that occured during the second fiscal quarter of the period covered by this report that has materially affected, or is reasonably likely to materially affect, the registrant’s internal control over financial reporting.

There were no significant changes in the registrant’s internal control over financial reporting that occurred during the second fiscal quarter of the period covered by this report that have materially affected, or are reasonably likely to materially affect, the registrant’s internal control over financial reporting.

Item 12. Disclosure of Securities Lending Activities for Closed-End Management Investment Companies.

(a) If the registrant is a closed-end management investment company, provide the following dollar amounts of income and compensation related to the securities lending activities of the registrant during its most recent fiscal year:

N/A

(1) Gross income from securities lending activities;

N/A

(2) All fees and/or compensation for each of the following securities lending activities and related services: any share of revenue generated by the securities lending program paid to the securities lending agent(s) (revenue split); fees paid for cash collateral management services (including fees deducted from a pooled cash collateral reinvestment vehicle) that are not included in the revenue split; administrative fees that are not included in the revenue split; fees for indemnification that are not included in the revenue split; rebates paid to borrowers; and any other fees relating to the securities lending program that are not included in the revenue split, including a description of those other fees;

N/A

(3) The aggregate fees/compensation disclosed pursuant to paragraph (2); and

N/A

(4) Net income from securities lending activities (i.e., the dollar amount in paragraph (1) minus the dollar amount in paragraph (3)).

If a fee for a service is included in the revenue split, state that the fee is included in the revenue split.

N/A

(b) If the registrant is a closed-end management investment company, describe the services provided to the registrant by the securities lending agent in the registrants most recent fiscal year.

N/A

ITEM 13. EXHIBITS.

(a) File the exhibits listed below as part of this Form. Letter or number the exhibits in the sequence indicated.

(1) Any code of ethics, or amendment thereto, that is the subject of the disclosure required by Item 2, to the extent that the registrant intends to satisfy the Item 2 requirements through filing of an exhibit.

(2) A separate certification for each principal executive officer and principal financial officer of the registrant as required by Rule 30a-2(a) under the Act (17 CFR 270.30a-2(a)) , exactly as set forth below:

Filed herewith.

SIGNATURES

[See General Instruction F]

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

(Registrant) Pioneer Fund

By (Signature and Title)* /s/ Lisa M. Jones

Lisa M. Jones, President & Chief Executive Officer

Date September 4, 2020

Pursuant to the requirements of the Securities Exchange Act of 1934 and the Investment Company Act of 1940, this report has been signed below by the following persons on behalf of the registrant and in the capacities and on the dates indicated.

By (Signature and Title)* /s/ Lisa M. Jones

Lisa M. Jones, President & Chief Executive Officer

Date September 4, 2020

By (Signature and Title)* /s/ Mark E. Bradley

Mark E. Bradley, Treasurer & Chief Accounting & Financial Officer

Date September 4, 2020

* Print the name and title of each signing officer under his or her signature.