November 29, 2019

2019 Summary Prospectus

•  iShares Edge MSCI USA Size Factor ETF | SIZE |  NYSE ARCA

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 November 29, 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^® EDGE MSCI USA SIZE FACTOR ETF

Ticker: SIZE Stock Exchange: NYSE Arca

Investment Objective

The iShares Edge MSCI USA Size Factor ETF (the “Fund”) seeks to track the investment results of an index composed of U.S. large- and mid-capitalization stocks with relatively smaller average market capitalization.

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
0.15%	None	0.00%	0.15%

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	5 Years	10 Years
$15	$48	$85	$192

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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. During the most recent fiscal year, the Fund's portfolio turnover rate was 30% of the average value of its portfolio.

Principal Investment Strategies

The Fund seeks to track the investment results of the MSCI USA Low Size Index (the “Underlying Index”), which is based on a traditional market capitalization-weighted parent index, the MSCI USA Index (the “Parent Index”). The Parent Index includes U.S. large- and mid-capitalization stocks, as defined by MSCI Inc. (the “Index Provider” or “MSCI”). The Underlying Index is constructed by applying a mathematical formula at each rebalancing that reweights the components of its market capitalization-weighted Parent Index, such that the representation of smaller capitalization companies is increased relative to larger capitalization companies. In addition, at each rebalancing, the Index Provider calculates a “constraint factor” for each component. The constraint factor is the ratio of the component’s weight in the Underlying Index to that component’s weight in the Parent Index. The constraint factor is held constant between each rebalancing, except in the case of corporate events (as defined by the Index Provider). Changes in the

relative weight of an individual component in the Parent Index due to market appreciation/depreciation result in that component increasing/decreasing in weight in the Underlying Index to hold the constraint factor for that component constant between each rebalancing. The Underlying Index is rebalanced semi-annually in May and November. As of July 31, 2019, there are 639 component securities in the Underlying Index. As of July 31, 2019, a significant portion of the Underlying Index is represented by securities of companies in the technology industry or sector. The components of the Underlying Index are likely to change over time.

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

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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 and Parent Index are sponsored by MSCI, which is independent of the Fund and BFA. The Index Provider determines the composition and relative weightings of the securities in the Underlying Index and Parent Index and publishes information regarding the market value of the Underlying Index and Parent 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 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.

Authorized Participant Concentration Risk. Only an Authorized Participant (as defined in the Creation and Redemptions section of this prospectus (the “Prospectus”)) 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

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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 of a particular issuer or issuers, country, group of countries, region, market, industry, group of industries, sector or asset class.

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, 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.

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

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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 Risk. The Underlying Index is designed to select stocks, in part, based on whether they are low size. The stocks of smaller mid-capitalization companies (“low size companies”) may be less stable and more susceptible to adverse developments, and their securities may be more volatile and less liquid, than those on the larger end of the mid-capitalization range or those of large-capitalization companies. The Fund will invest in low size companies to approximately the same extent that they are represented in the Underlying Index.

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.

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.

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

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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.

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.

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Performance Information

The bar chart and table that follow show how the Fund has performed on a calendar year basis and provide an indication of the risks of investing in the Fund. Both assume that all dividends and distributions have been reinvested in the Fund. Past performance (before and after taxes) does not necessarily indicate how the Fund will perform in the future. Supplemental information about the Fund’s performance is shown under the heading Total Return Information in the Supplemental Information section of the Prospectus.

Year by Year Returns¹ (Years Ended December 31)

¹ The Fund’s year-to-date return as of September 30, 2019 was 19.92%.

The best calendar quarter return during the periods shown above was 7.39% in the 4th quarter of 2014; the worst was -12.49% in the 4th quarter of 2018.

Updated performance information, including the Fund’s current NAV, may be obtained by visiting our website at www.iShares.com or by calling 1-800-iShares (1-800-474-2737) (toll free).

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Average Annual Total Returns

(for the periods ended December 31, 2018)

	One Year	Five Years	Since Fund Inception
(Inception Date: 4/16/2013)
Return Before Taxes	-6.51%	7.92%	9.62%
Return After Taxes on Distributions1	-7.04%	7.39%	9.08%
Return After Taxes on Distributions and Sale of Fund Shares1	-3.49%	6.17%	7.59%
MSCI USA Risk Weighted Index (Index returns do not reflect deductions for fees, expenses, or taxes)2	-5.19%	8.34%	10.02%
MSCI USA Low Size Index (Index returns do not reflect deductions for fees, expenses, or taxes)2	N/A	N/A	N/A

¹ After-tax returns in the table above are calculated using the historical highest individual U.S. federal marginal income tax rates and do not reflect the impact of state or local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown, and after-tax returns shown are not relevant to tax-exempt investors or investors who hold shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts (“IRAs”). Fund returns after taxes on distributions and sales of Fund shares are calculated assuming that an investor has sufficient capital gains of the same character from other investments to offset any capital losses from the sale of Fund shares. As a result, Fund returns after taxes on distributions and sales of Fund shares may exceed Fund returns before taxes and/or returns after taxes on distributions.

² On December 3, 2018, the Fund’s Underlying Index changed from the MSCI USA Risk Weighted Index to the MSCI USA Low Size Index. The inception date of the MSCI USA Low Size Index was September 11, 2018.

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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. Hsui and Mr. Savage have been Portfolio Managers of the Fund since 2013. Mr. Mason has been a Portfolio Manager of the Fund since 2016. Ms. Aguirre and Ms. Whitelaw have been Portfolio Managers of the Fund since 2018.

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 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-SIZE-1119

Investment Company Act file No.: 811-09729