January 15, 2020

2020 Summary Prospectus

•  iShares Factors US Growth Style ETF | STLG | CBOE BZX

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 (including amendments and supplements) and other information about the Fund, including the Fund’s statement of additional information and shareholder report, online at https://www.ishares.com/prospectus. You can also get this information at no cost by calling 1-800-iShares (1-800-474-2737) or by sending an e-mail request to iSharesETFs@blackrock.com, or from your financial professional. The Fund’s prospectus and statement of additional information, both dated December 19, 2019, as amended and supplemented from time to time, are incorporated by reference into (legally made a part of) this Summary Prospectus.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission (“SEC”), 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 your financial intermediary, such as a broker-dealer or bank. 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. If you hold accounts through a financial intermediary, you may contact your financial intermediary to enroll in electronic delivery. Please note that not all financial intermediaries may offer this service.

You may elect to receive all future reports in paper free of charge. If you hold accounts through a financial intermediary, you can follow the instructions included with this disclosure, if applicable, or contact your financial intermediary to request that you continue to receive paper copies of your shareholder reports. Please note that not all financial intermediaries may offer this service. Your election to receive reports in paper will apply to all funds held with your financial intermediary.

The SEC has not approved or disapproved these securities or passed upon the adequacy of this prospectus. Any representation to the contrary is a criminal offense.

iSHARES^® FACTORS US GROWTH STYLE ETF

Ticker: STLG Stock Exchange: Cboe BZX

Investment Objective

The iShares Factors US Growth Style ETF (the “Fund”) seeks to track the investment results of an index composed of U.S. large- and mid-capitalization stocks with favorable exposure to target style factors subject to constraints.

Fees and Expenses

The following table describes the fees and expenses that you will incur if you own shares of the Fund. The investment advisory agreement between iShares Trust (the “Trust”) and BlackRock Fund Advisors (“BFA”) (the “Investment Advisory Agreement”) provides that BFA will pay all operating expenses of the Fund, except the management fees, interest expenses, taxes, expenses incurred with respect to the acquisition and disposition of portfolio securities and the execution of portfolio transactions, including brokerage commissions, distribution fees or expenses, litigation expenses and any extraordinary expenses.

You may also incur usual and customary brokerage commissions and other charges when buying or selling shares of the Fund, which are not reflected in the Example that follows:

Annual Fund Operating Expenses (ongoing expenses that you pay each year as a percentage of the value of your investments)
Management Fees	Distribution and Service (12b-1) Fees	Other Expenses1	Total Annual Fund Operating Expenses
0.25%	None	0.00%	0.25%

¹ The amount rounded to 0.00%.

Example. This Example is intended to help you compare the cost of owning shares of the Fund with the cost of investing in other funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then sell all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions, your costs would be:

1 Year	3 Years
$26	$80

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Portfolio Turnover. The Fund may pay 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 the Annual Fund Operating Expenses or in the Example, affect the Fund’s performance.

Principal Investment Strategies

The Fund seeks to track the investment results of the Russell US Large Cap Factors Growth Style Index (the “Underlying Index”), which is an objective-rules based equity index provided by FTSE Russell (the “Index Provider” or “Russell”). The Underlying Index is designed to select equity securities from the Russell 1000^® Growth Index (the “Parent Index”), which in turn is a subset of the Russell 1000^® Index (the “Russell 1000”). The Underlying Index is designed to select equity securities from the Parent Index with exposure to five equity style factors (momentum, quality, value, size, and low volatility) while maintaining a level of risk similar to that of the Parent Index. The Parent Index focuses on growth by selecting the equity securities of Russell 1000 issuers with higher two-year growth forecasts and higher sales per share growth over the past five years, each relative to all issuers within the Russell 1000. The Index Provider uses the Institutional Brokers’ Estimate System (I/B/E/S) database to forecast growth.The Underlying Index includes large- and mid-capitalization companies, as defined by the Index Provider.

Russell, in selecting equity securities from the Parent Index, assigns a weighted composite score to each security using a proprietary model based on five commonly-used equity style factors (momentum, quality, value, size, and low volatility). The value score is calculated from the following value factor metrics: 12-month trailing book-to-price, dividend yield, earnings yield and cash flow yield (i.e., cash flow divided by the full market capitalization). The momentum score is calculated from three momentum factor metrics: price momentum, earnings momentum and earnings announcement drift (i.e., the difference between a stock's performance on and immediately following an earnings announcement date). The quality score is calculated from four quality factor metrics: gross profitability, dilution, accruals and changes in net operating assets. The low volatility score is calculated based on a 12-month trailing realized volatility, and the size score seeks to measure the market capitalization of each company as compared to other companies of the Parent Index.

As of December 13, 2019, the Underlying Index consisted of 129 component securities. As of December 13, 2019, a significant portion of the Underlying Index is represented by securities of companies in the consumer services and technology industries or sectors. The components of the Underlying Index are likely to change over time.

The Underlying Index is reviewed monthly using an optimization process designed to maximize, in aggregate, the Underlying Index's exposure to the weighted combination of five target investment style factors while

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maintaining a total risk similar to that of the Parent Index.

BFA uses a “passive” or indexing approach to try to achieve the Fund’s investment objective. Unlike many investment companies, the Fund does not try to “beat” the index it tracks and does not seek temporary defensive positions when markets decline or appear overvalued.

Indexing may eliminate the chance that the Fund will substantially outperform the Underlying Index but also may reduce some of the risks of active management, such as poor security selection. Indexing seeks to achieve lower costs and better after-tax performance by aiming to keep portfolio turnover low in comparison to actively managed investment companies.

BFA uses a representative sampling indexing strategy to manage the Fund. “Representative sampling” is an indexing strategy that involves investing in a representative sample of securities that collectively has an investment profile similar to that of an applicable underlying index. The securities selected are expected to have, in the aggregate, investment characteristics (based on factors such as market capitalization and industry weightings), fundamental characteristics (such as return variability and yield) and liquidity measures similar to those of an applicable underlying index. The Fund may or may not hold all of the securities in the Underlying Index.

The Fund generally will invest at least 90% of its assets in the component securities of the Underlying Index and may invest up to 10% of its assets in certain futures, options and swap contracts, cash and cash equivalents, including shares of money market funds

advised by BFA or its affiliates, as well as in securities not included in the Underlying Index, but which BFA believes will help the Fund track the Underlying Index. The Fund seeks to track the investment results of the Underlying Index before fees and expenses of the Fund.

The Fund may lend securities representing up to one-third of the value of the Fund's total assets (including the value of any collateral received).

The Underlying Index is sponsored by Russell, which is part of the London Stock Exchange Group and is independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and publishes information regarding the market value of the Underlying Index.

Industry Concentration Policy. The Fund will concentrate its investments (i.e., hold 25% or more of its total assets) in a particular industry or group of industries to approximately the same extent that the Underlying Index is concentrated. For purposes of this limitation, securities of the U.S. government (including its agencies and instrumentalities) and repurchase agreements collateralized by U.S. government securities are not considered to be issued by members of any industry.

Summary of Principal Risks

As with any investment, you could lose all or part of your investment in the Fund, and the Fund's performance could trail that of other investments. The Fund is subject to certain risks, including the principal risks noted below, any of which may adversely affect the Fund's

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net asset value per share (“NAV”), trading price, yield, total return and ability to meet its investment objective. The order of the below risk factors does not indicate the significance of any particular risk factor.

Asset Class Risk. Securities and other assets in the Underlying Index or in the Fund's portfolio may underperform in comparison to the general financial markets, a particular financial market or other asset classes.

Assets Under Management (AUM) Risk. From time to time, an Authorized Participant (as defined in the Creations and Redemptions section of this prospectus (the “Prospectus”)), a third-party investor, the Fund’s adviser or an affiliate of the Fund’s adviser, or a fund may invest in the Fund and hold its investment for a specific period of time to allow the Fund to achieve size or scale. Therecan be no assurance that any such entity would not redeem its investment or that the size of the Fund would be maintained at such levels, which could negatively impact the Fund.

Authorized Participant Concentration Risk. Only an Authorized Participant may engage in creation or redemption transactions directly with the Fund, and none of those Authorized Participants is obligated to engage in creation and/or redemption transactions. The Fund has a limited number of institutions that may act as Authorized Participants on an agency basis (i.e., on behalf of other market participants). To the extent that Authorized Participants exit the business or are unable to proceed with creation or redemption orders with respect to the Fund and no other Authorized Participant is able to step forward to create or redeem Creation Units (as defined in the Purchase and

Sale of Fund Shares section of the Prospectus), Fund shares may be more likely to trade at a premium or discount to NAV and possibly face trading halts or delisting.

Calculation Methodology Risk. The Underlying Index relies on various sources of information to assess the criteria of issuers included in the Underlying Index, including information that may be based on assumptions and estimates. Neither the Fund nor BFA can offer assurances that the Underlying Index’s calculation methodology or sources of information will provide an accurate assessment of included issuers.

Concentration Risk. The Fund may be susceptible to an increased risk of loss, including losses due to adverse events that affect the Fund’s investments more than the market as a whole, to the extent that the Fund's investments are concentrated in the securities and/or other assets of a particular issuer or issuers, country, group of countries, region, market, industry, group of industries, sector or asset class.

Consumer Services Industry Risk. Companies in the consumer services industry may be affected by, among other things, changes in the domestic and international economies, exchange rates, competition, consumers' disposable income and consumer preferences. Companies in the consumer services industry are facing increased government and regulatory scrutiny and may be subject to adverse government or regulatory action.

Cybersecurity Risk. Failures or breaches of the electronic systems of the Fund, the Fund's adviser, distributor, the Index Provider and other service providers, market makers,

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Authorized Participants or the issuers of securities in which the Fund invests have the ability to cause disruptions, negatively impact the Fund’s business operations and/or potentially result in financial losses to the Fund and its shareholders. While the Fund has established business continuity plans and risk management systems seeking to address system breaches or failures, there are inherent limitations in such plans and systems. Furthermore, the Fund cannot control the cybersecurity plans and systems of the Fund’s Index Provider and other service providers, market makers, Authorized Participants or issuers of securities in which the Fund invests.

Equity Securities Risk. Equity securities are subject to changes in value, and their values may be more volatile than those of other asset classes. The Underlying Index is comprised of common stocks, which generally subject their holders to more risks than preferred stocks and debt securities because common stockholders’ claims are subordinated to those of holders of preferred stocks and debt securities upon the bankruptcy of the issuer.

Growth Securities Risk. The Fund invests in growth securities, which may be more volatile than other types of investments, may perform differently than the market as a whole and may underperform when compared to securities with different investment parameters. Under certain market conditions, growth securities have performed better during the later stages of economic recovery (although there is no guarantee that they will continue to do so). Therefore, growth securities may go in and out of favor over time.

Index-Related Risk. There is no guarantee that the Fund’s investment results will have a high degree of correlation to those of the Underlying Index or that the Fund will achieve its investment objective. Market disruptions and regulatory restrictions could have an adverse effect on the Fund’s ability to adjust its exposure to the required levels in order to track the Underlying Index. Errors in index data, index computations or the construction of the Underlying Index in accordance with its methodology may occur from time to time and may not be identified and corrected by the Index Provider for a period of time or at all, which may have an adverse impact on the Fund and its shareholders.

Issuer Risk. The performance of the Fund depends on the performance of individual securities to which the Fund has exposure. Changes in the financial condition or credit rating of an issuer of those securities may cause the value of the securities to decline.

Large-Capitalization Companies Risk. Large-capitalization companies may be less able than smaller capitalization companies to adapt to changing market conditions. Large-capitalization companies may be more mature and subject to more limited growth potential compared with smaller capitalization companies. During different market cycles, the performance of large-capitalization companies has trailed the overall performance of the broader securities markets.

Low Size Strategy Risk. Companies with relatively lower market capitalization within a broader index or market capitalization range (“low size companies”) may be less stable and more susceptible to adverse developments, and their securities may be more volatile and less liquid, than companies with relatively higher market capitalization.

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Management Risk. As the Fund will not fully replicate the Underlying Index, it is subject to the risk that BFA's investment strategy may not produce the intended results.

Market Risk. The Fund could lose money over short periods due to short-term market movements and over longer periods during more prolonged market downturns.

Market Trading Risk. The Fund faces numerous market trading risks, including the potential lack of an active market for Fund shares, losses from trading in secondary markets, periods of high volatility and disruptions in the creation/redemption process. ANY OF THESE FACTORS, AMONG OTHERS, MAY LEAD TO THE FUND'S SHARES TRADING AT A PREMIUM OR DISCOUNT TO NAV.

Mid-Capitalization Companies Risk. Compared to large-capitalization companies, mid-capitalization companies may be less stable and more susceptible to adverse developments. In addition, the securities of mid-capitalization companies may be more volatile and less liquid than those of large-capitalization companies.

Minimum Volatility  Strategy Risk. Although the Underlying Index was created by the Index Provider to seek high exposure to the four style factors while maintaining a risk similar to that of the Parent Index, there is no guarantee that the Index Provider will be successful. Securities in the Fund's portfolio may be subject to price volatility, and the prices may not be any less volatile than the market as a whole, and could be more volatile.

Model Risk. Neither the Fund nor BFA can offer assurances that the Index Provider’s model will result in the Fund meeting its investment objective. The Fund may underperform other funds that do not similarly invest.

Momentum Strategy Risk. Stocks that previously exhibited high momentum characteristics may not experience positive momentum or may experience more volatility than the market as a whole.

Non-Diversification Risk. The Fund may invest a large percentage of its assets in securities issued by or representing a small number of issuers. As a result, the Fund's performance may depend on the performance of a small number of issuers.

Operational Risk. The Fund is exposed to operational risks arising from a number of factors, including, but not limited to, human error, processing and communication errors, errors of the Fund’s service providers, counterparties or other third-parties, failed or inadequate processes and technology or systems failures. The Fund and BFA seek to reduce these operational risks through controls and procedures. However, these measures do not address every possible risk and may be inadequate to address significant operational risks.

Passive Investment Risk. The Fund is not actively managed, and BFA generally does not attempt to take defensive positions under any market conditions, including declining markets.

Quality Strategy Risk. Stocks included in the Underlying Index are deemed by the Index Provider to be quality stocks, but there is no guarantee that the past performance of these stocks will continue. Companies that issue these

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stocks may experience lower than expected returns or may experience negative growth, as well as increased leverage, resulting in lower than expected or negative returns to Fund shareholders. Many factors can affect a stock’s quality and performance, and the impact of these factors on a stock or its price can be difficult to predict.

Risk of Investing in the U.S. Certain changes in the U.S. economy, such as when the U.S. economy weakens or when its financial markets decline, may have an adverse effect on the securities to which the Fund has exposure.

Securities Lending Risk. The Fund may engage in securities lending. Securities lending involves the risk that the Fund may lose money because the borrower of the loaned securities fails to return the securities in a timely manner or at all. The Fund could also lose money in the event of a decline in the value of collateral provided for loaned securities or a decline in the value of any investments made with cash collateral. These events could also trigger adverse tax consequences for the Fund.

Small Fund Risk. When the Fund’s size is small, the Fund may experience low trading volume and wide bid/ask spreads. In addition, the Fund may face the risk of being delisted if the Fund does not meet certain conditions of the listing exchange. Any resulting liquidation of the Fund could cause the Fund to incur elevated transaction costs for the Fund and negative tax consequences for its shareholders.

Technology Sector Risk. Technology companies, including information technology companies, may have limited product lines, markets, financial resources or personnel. Technology companies typically face intense

competition and potentially rapid product obsolescence. They are also heavily dependent on intellectual property rights and may be adversely affected by the loss or impairment of those rights. Companies in the technology sector are facing increased government and regulatory scrutiny and may be subject to adverse government or regulatory action.

Tracking Error Risk. The Fund may be subject to tracking error, which is the divergence of the Fund’s performance from that of the Underlying Index. Tracking error may occur because of differences between the securities and other instruments held in the Fund’s portfolio and those included in the Underlying Index, pricing differences, transaction costs incurred by the Fund, the Fund’s holding of uninvested cash, differences in timing of the accrual of or the valuation of dividends or interest, the requirements to maintain pass-through tax treatment, portfolio transactions carried out to minimize the distribution of capital gains to shareholders, changes to the Underlying Index or the costs to the Fund of complying with various new or existing regulatory requirements. This risk may be heightened during times of increased market volatility or other unusual market conditions. Tracking error also may result because the Fund incurs fees and expenses, while the Underlying Index does not. BFA EXPECTS THAT THE FUND MAY EXPERIENCE HIGHER TRACKING ERROR THAN IS TYPICAL FOR SIMILAR INDEX ETFs, ESPECIALLY BEFORE THE FUND REACHES SUFFICIENT SCALE AND FURTHER BROADENS ITS HOLDINGS.

Value Strategy Risk. Securities issued by companies that may be perceived as

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undervalued, particularly securities of a company that appear to trade at a significant discount to the company’s intrinsic value, may fail to appreciate for long periods of time and may never realize their full potential value. The Index Provider may be unsuccessful in creating an index that emphasizes undervalued securities. Value securities have generally performed better than non-value securities during periods of economic recovery (although there is no

assurance that they will continue to do so). Value securities may go in and out of favor over time.

Performance Information

As of the date of the Prospectus, the Fund has been in operation for less than one full calendar year and therefore does not report its performance information.

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Management

Investment Adviser. BlackRock Fund Advisors.

Portfolio Managers. Rachel Aguirre, Jennifer Hsui, Alan Mason, Greg Savage and Amy Whitelaw (the “Portfolio Managers”) are primarily responsible for the day-to-day management of the Fund. Each Portfolio Manager supervises a portfolio management team. Ms. Aguirre, Ms. Hsui, Mr. Mason, Mr. Savage and Ms. Whitelaw have been Portfolio Managers of the Fund since inception.

Purchase and Sale of Fund Shares

The Fund is an exchange-traded fund (commonly referred to as an “ETF”). Individual shares of the Fund are listed on a national securities exchange. Most investors will buy and sell shares of the Fund through a broker-dealer. The price of Fund shares is based on market price, and because ETF shares trade at market prices rather than at NAV, shares may trade at a price greater than NAV (a premium) or less than NAV (a discount). The Fund will only issue or redeem shares that have been aggregated into blocks of 50,000 shares or multiples thereof (“Creation Units”) to Authorized Participants who have entered into agreements with the Fund's distributor. The Fund generally will issue or redeem Creation Units in return for a designated portfolio of securities (and an amount of cash) that the Fund specifies each day.

Tax Information

The Fund intends to make distributions that may be taxable to you as ordinary income or capital gains, unless you are investing through a tax-deferred arrangement such as a 401(k) plan or an individual retirement account (“IRA”), in which case, your distributions generally will be taxed when withdrawn.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), BFA or other related companies may pay the intermediary for marketing activities and presentations, educational training programs, conferences, the development of technology platforms and reporting systems or other services related to the sale or promotion of the Fund. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary’s website for more information.

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For more information visit www.iShares.com or call 1-800-474-2737

IS-SP-STLG-0120

Investment Company Act file No.: 811-09729