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Janus Henderson International Opportunities Fund

Ticker: HFODX Class D Shares*

* Effective July 6, 2020, Class D Shares are open to new investors. Until that time, Class D Shares remain closed to new investors, with certain limited exceptions.

Summary Prospectus dated January 28, 2020
As Supplemented June 19, 2020

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus, reports to shareholders, and other information about the Fund online at janushenderson.com/reports. You can also get this information at no cost by calling a Janus Henderson representative at 1-800-525-3713 or by sending an email request to prospectusorder@janushenderson.com.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or your plan sponsor, broker-dealer, or financial intermediary, or if you invest directly with the Fund, by contacting a Janus Henderson representative. Instead, the reports will be made available on a 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 from the Fund electronically by contacting your plan sponsor, broker-dealer, or financial intermediary, or if you invest directly with the Fund, by visiting janushenderson.com/edelivery.

You may elect to receive all future reports in paper free of charge. If you do not invest directly with the Fund, you should contact your plan sponsor, broker-dealer, or financial intermediary, to request to continue receiving paper copies of your shareholder reports. If you invest directly with the Fund, you can call 1-800-525-3713 to let the Fund know that you wish to continue receiving paper copies of your shareholder reports. Your election to receive reports in paper will apply to all Janus Henderson mutual funds where held (i.e., all Janus Henderson mutual funds held in your account if you invest through your financial intermediary or all Janus Henderson mutual funds held with the fund complex if you invest directly with a fund).

Investment Objective

Janus Henderson International Opportunities Fund seeks long-term capital appreciation primarily through investment in equities of non-U.S. companies.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)	Class D
Management Fees	0.98%
Other Expenses	0.61%
Total Annual Fund Operating Expenses(1)	1.59%
Fee Waiver(1)	0.53%
Total Annual Fund Operating Expenses After Fee Waiver(1)	1.06%

(1)  Janus Capital has contractually agreed to waive its investment advisory fee and/or reimburse operating expenses to the extent that the Fund’s total annual fund operating expenses (excluding administrative services fees (including out-of-pocket costs), brokerage commissions, interest, dividends, taxes, acquired fund fees and expenses, and extraordinary expenses) exceed 0.88% for at least a one-year period commencing on January 28, 2020. The contractual waiver may be terminated or modified prior to this date only at the discretion of the Board of Trustees.

EXAMPLE:

The following Example is based on expenses without waivers. The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating

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expenses without waivers remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class D Shares	$ 162	$ 502	$ 866	$ 1,889

Portfolio Turnover: The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 45% of the average value of its portfolio.

Principal investment strategies

The Fund pursues its investment objective by investing, under normal circumstances, approximately 70% of its net assets (plus any borrowings for investment purposes) in equity securities of non-U.S. companies and in at least three different countries. Equity securities include common stocks and related securities, such as preferred stock, convertible securities, and depositary receipts. Non-U.S. companies include companies in emerging market countries and are broadly defined to include any company that meets one of the following tests: (i) its country of organization, its primary business office and/or the principal trading market of its stock are located outside of the United States, (ii) 50% or more of its assets are located in a country other than the United States, or (iii) 50% or more of its revenues are derived from outside of the United States.

Fund investment performance will be derived primarily from stock selection. A strategic asset allocation process will be a secondary contributor to the investment process. Security selection may be based upon an analysis of a company’s valuations relative to earnings forecasts or other valuation criteria, earnings growth prospects of a company, the quality of a company’s management and the unique competitive advantages of a company. Asset allocation will be reviewed regularly based upon strategic views related to the growth prospects, valuations and pricing associated with international equity regions. Assets of the Fund are allocated to teams of investment personnel, referred to as “sleeve portfolio managers,” who have experience with respect to a particular geographic region or discipline.

The Fund generally sells a stock when, in the portfolio managers’ opinion, there is a deterioration in the company’s fundamentals, the company fails to meet performance expectations, the stock achieves its target price, its earnings are disappointing or its revenue growth has slowed. The Fund may also sell a stock if the portfolio managers believe that negative country or regional factors may affect the company’s outlook, in the portfolio managers’ opinion, a superior investment opportunity arises or to meet cash requirements. The portfolio managers anticipate that the Fund will continue to hold securities of companies that grow or expand so long as the portfolio managers believe the securities continue to offer prospects of long-term growth. Some of the Fund’s investments may produce income, although income from dividends and interest will be incidental and not an important consideration in choosing investments.

The Fund may, under unusual circumstances, invest in a single country or a limited number of countries. In addition, the Fund may invest in securities issued by smaller companies and in less seasoned issuers, including through initial public offerings and private placements.

The Fund may invest its assets in derivatives, which are instruments that have a value derived from, or directly linked to, an underlying asset, such as equity securities, commodities, or currencies, as substitutes for securities in which the Fund invests. In particular, the Fund may invest in derivatives such as forward currency contracts to offset risks associated with currency exposure.

The Fund does not limit its investments to companies of any particular size and may invest a significant portion of its assets in smaller and less seasoned issuers. However, in an attempt to reduce portfolio risks, the portfolio managers generally will invest across countries, industry groups and/or sectors.

Principal investment risks

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an international equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

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Market Risk.  The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money. Market risk may affect a single issuer, industry, economic sector, or the market as a whole.

Foreign Exposure Risk.  The Fund normally has significant exposure to foreign markets as a result of its investments in foreign securities and derivatives that provide exposure to foreign markets, including investments in emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. Some of the risks of investing directly in foreign securities may be reduced when the Fund invests indirectly in such securities through various other investment vehicles including derivatives, but such investments also involve other risks, as noted in the Fund’s Summary Prospectus. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Emerging Markets Risk.  The risks of foreign investing are heightened when investing in emerging markets. Emerging markets securities involve a number of additional risks, which may result from less government supervision and regulation of business and industry practices (including the potential lack of strict finance and accounting controls and standards), stock exchanges, brokers, and listed companies, making these investments potentially more volatile in price and less liquid than investments in developed securities markets, resulting in greater risk to investors. There is a risk in developing countries that a future economic or political crisis could lead to price controls, forced mergers of companies, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, seizure, nationalization, sanctions or imposition of restrictions by various governmental entities on investment and trading, or creation of government monopolies, any of which may have a detrimental effect on the Fund’s investments. In addition, the Fund’s investments may be denominated in foreign currencies and therefore, changes in the value of a country’s currency compared to the U.S. dollar may affect the value of the Fund’s investments. To the extent that the Fund invests a significant portion of its assets in the securities of emerging markets issuers in or companies of a single country or region, it is more likely to be impacted by events or conditions affecting that country or region, which could have a negative impact on the Fund’s performance. Additionally, foreign and emerging market risks, including but not limited to price controls, expropriation or confiscatory taxation, imposition or enforcement of foreign ownership limits, nationalization, and restrictions on repatriation of assets may be heightened to the extent the Fund invests in Chinese local market securities. Some of the risks of investing directly in emerging market securities may be reduced when the Fund invests indirectly in such securities through various other investment vehicles including derivatives, as noted in the Fund’s Summary Prospectus, but such investments also involve other risks. As of September 30, 2019, approximately 19.1% of the Fund’s investments were in emerging markets (i.e., countries included in the MSCI Emerging Markets Index^sm).

Industry and Sector Risk.  Although the Fund does not concentrate its investments in specific industries or industry sectors, at times, it may have a significant portion of its assets invested in securities of companies conducting similar business or business within the same economic sector. Companies in the same industry or economic sector may be similarly affected by economic or market events, making the Fund more vulnerable to unfavorable developments than funds that invest more broadly. As the Fund’s portfolio becomes more concentrated, the Fund is less able to spread risk and potentially reduce the risk of loss and volatility. In addition, the Fund may be overweight or underweight in certain industries or sectors relative to its benchmark index, which may cause the Fund’s performance to be more or less sensitive to developments affecting those sectors.

Geographic Concentration Risk.  To the extent the Fund invests a substantial amount of its assets in issuers located in a single country or region, the economic, political, social, regulatory, or other developments or conditions within such country or region will generally have a greater effect on the Fund than they would on a more geographically diversified fund, which may result in greater losses and volatility. Adverse developments in certain regions could also adversely affect securities of other countries whose economies appear to be unrelated and could have a negative impact on the Fund’s performance.

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Small- and Mid-Sized Companies Risk.  The Fund’s investments in securities issued by small- and mid-sized companies, which can include smaller, start-up companies offering emerging products or services, may involve greater risks than are customarily associated with larger, more established companies. For example, while small- and mid-sized companies may realize more substantial growth than larger or more established issuers, they may also suffer more significant losses as a result of their narrow product lines, limited operating history, greater exposure to competitive threats, limited financial resources, limited trading markets, and the potential lack of management depth. Securities issued by small- and mid-sized companies tend to be more volatile and somewhat more speculative than securities issued by larger or more established companies and may underperform as compared to the securities of larger or more established companies. These holdings are also subject to wider price fluctuations and tend to be less liquid than stocks of larger or more established companies, which could have a significant adverse effect on the Fund’s returns, especially as market conditions change.

Initial Public Offering Risk.  The Fund’s purchase of shares issued in an initial public offering (“IPO”) exposes it to the risks associated with companies that have little operating history as public companies, as well as to the risks inherent in those sectors of the market where these new issuers operate. Although IPO investments may have had a positive impact on the Fund’s performance in the past, there can be no assurance that the Fund will identify favorable IPO investment opportunities in the future. In addition, as the Fund increases in size, the impact of IPOs on the Fund’s performance will generally decrease.

Derivatives Risk.  Derivatives can be highly volatile and involve risks in addition to the risks of the underlying referenced securities or asset. Gains or losses from a derivative investment can be substantially greater than the derivative’s original cost, and can therefore involve leverage. Leverage may cause the Fund to be more volatile than if it had not used leverage. Derivatives can be less liquid than other types of investments and entail the risk that the counterparty will default on its payment obligations. The Fund may use derivatives, including forward currency contracts, for hedging purposes. Hedging with derivatives may increase expenses, and there is no guarantee that a hedging strategy will work. While hedging can reduce or eliminate losses, it can also reduce or eliminate gains or cause losses if the market moves in a manner different from that anticipated by the portfolio managers or if the cost of the derivative outweighs the benefit of the hedge.

Management Risk.  The Fund is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies employed for the Fund may fail to produce the intended results. The Fund may underperform its benchmark index or other mutual funds with similar investment objectives.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance information

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on June 5, 2017. The performance shown for Class D Shares for periods prior to June 5, 2017, reflects the performance of Class A Shares of Henderson International Opportunities Fund (the “Predecessor Fund”), calculated using the fees and expenses of Class A Shares of the Predecessor Fund (without sales charges), net of any applicable fee and expense limitations or waivers. The Predecessor Fund was advised by Henderson Global Investors (North America) Inc. and subadvised by Henderson Investment Management Limited. Class A Shares, Class C Shares, Class R Shares, Class I Shares, Class IF Shares, and Class R6 Shares of the Predecessor Fund were reorganized into Class A Shares, Class C Shares, Class R Shares, Class I Shares (Class I Shares and Class IF Shares of the Predecessor Fund were reorganized into Class I Shares of the Fund), and Class N Shares, respectively, of the Fund on June 2, 2017. In connection with this reorganization, certain shareholders of the Predecessor Fund who held shares directly with the Predecessor Fund and not through an intermediary had the Class A Shares, Class C Shares, Class R Shares, Class I Shares, and Class N Shares of the Fund received in the merger automatically exchanged for Class D Shares of the Fund following the merger. If Class D Shares of the Fund had been available during periods prior to June 5, 2017, the performance shown may have been different because the Fund and the Predecessor Fund have different expenses. The performance shown for the periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. All figures assume

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reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s (and the Predecessor Fund’s) past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Updated performance information is available at janushenderson.com/allfunds or by calling 1-800-525-3713.

Annual Total Returns for Class D Shares (calendar year-end)

Best Quarter: 1st Quarter 2012 16.30% Worst Quarter: 3rd Quarter 2011 – 21.11%

Average Annual Total Returns (periods ended 12/31/19)
	1 Year	5 Years	10 Years	Since Inception (8/31/01)
Class D Shares
Return Before Taxes	26.58%	4.11%	5.15%	8.10%
Return After Taxes on Distributions	25.71%	3.14%	4.71%	7.58%
Return After Taxes on Distributions and Sale of Fund Shares(1)	16.79%	3.22%	4.24%	6.93%
MSCI ACWI ex-USA Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)	21.51%	5.51%	4.97%	6.25%
MSCI EAFE® Index (reflects no deduction for expenses, fees, or taxes, except foreign withholding taxes)	22.01%	5.67%	5.50%	5.65%

(1)  If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.

Effective January 28, 2020, the Fund’s primary benchmark index changed from the MSCI EAFE Index to the MSCI ACWI ex-USA Index. Janus Capital believes that the MSCI ACWI ex-USA Index represents a more appropriate benchmark for the Fund, given its exposure to developing markets. The indices are described below.

• The MSCI ACWI ex-USA Index is an unmanaged, free float-adjusted, market capitalization weighted index composed of stocks of large and mid-cap companies located in countries throughout the world, excluding the United States.

• The MSCI EAFE (Europe, Australasia, Far East) Index is a free float-adjusted market capitalization index designed to measure developed market equity performance. The MSCI EAFE Index is composed of companies representative of the market structure of developed market countries.

After-tax returns are calculated using distributions for the Predecessor Fund’s Class A Shares for the period prior to June 5, 2017. If Class D Shares of the Fund had been available during periods prior to June 5, 2017, the distributions used to calculate the after-tax returns may have been different. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-advantaged account, such as a 401(k) plan or an IRA.

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Management

Investment Adviser:  Janus Capital Management LLC

Portfolio Managers: Dean Cheeseman is Lead Portfolio Manager of the Fund, and has been a member of the Fund’s portfolio management team since March 2019. Paul O’Connor is Executive Vice President and Portfolio Manager of the Fund, and has been a member of the Fund’s portfolio management team since April 2016.

Purchase and sale of Fund shares

Minimum Investment Requirements
To open a new regular Fund account	$2,500
To open a new regular Fund account with an automatic investment program of $50 per month	$ 100
To open a new UGMA/UTMA account, Coverdell Education Savings Account, or a retirement Fund account
• without an automatic investment program	$1,000
• with an automatic investment program of $50 per month	$ 100
To add to any existing type of Fund account without an automatic investment program	$ 50

You may generally purchase, exchange, or redeem Fund Shares on any business day by written request, wire transfer, telephone, and in most cases, online at janushenderson.com/individual. You may conduct transactions by mail (Janus Henderson, P.O. Box 219109, Kansas City, MO 64121-9109), or by telephone at 1-800-525-3713. Purchase, exchange, or redemption requests must be received in good order by the Fund or its agents prior to the close of the regular trading session of the New York Stock Exchange in order to receive that day’s net asset value. For additional information, refer to “To Open an Account or Buy Shares,” “To Exchange Shares,” and/or “To Sell Shares” in the Prospectus.

Tax information

The Fund’s distributions are taxable, and will be taxed as ordinary income or capital gains, unless you are investing through a tax-advantaged arrangement, such as a 401(k) plan or an individual retirement account (in which case you may be taxed upon withdrawal of your investment from such account).

Payments to broker-dealers and other financial intermediaries

With respect to share classes not offered in this Prospectus, the Fund and its related companies pay select broker-dealer firms or other financial intermediaries for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing a broker-dealer or other intermediary or a salesperson to recommend the Fund over another investment or to recommend one share class over another.

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