iShares MSCI Total International Index Fund

iShares MSCI Total International Index Fund - Class K

APRIL 30, 2018

Summary Prospectus

BlackRock Funds III | Class K Shares

►	iShares MSCI Total International Index Fund
	Class K: BDOKX

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 http://www.blackrock.com/prospectus. You can also get this information at no cost by calling (800) 537-4942 or by sending an e-mail request to prospectus.request@blackrock.com, or from your financial professional. The Fund’s prospectus and statement of additional information, both dated April 30, 2018, as amended and supplemented from time to time, are incorporated by reference into (legally made a part of) this Summary Prospectus.

This Summary Prospectus contains information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference.

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Summary Prospectus. Any representation to the contrary is a criminal offense.

Not FDIC Insured • May Lose Value • No Bank Guarantee

Summary Prospectus

Key Facts About iShares MSCI Total International Index Fund

Investment Objective

The investment objective of iShares MSCI Total International Index Fund (formerly known as BlackRock Total International ex. U.S. Index Fund) (“Total International Index Fund” or the “Fund”), a series of BlackRock Funds III (the “Trust”), is to match the performance of the MSCI All Country World ex USA Index (the “MSCI ACWI ex USA Index” or the “Underlying Index”) in U.S. dollars with net dividends as closely as possible before the deduction of Fund expenses.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Class K Shares of the Total International Index Fund.

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)¹		Class K Shares
Management Fee^1,2		0.03%
Distribution and/or Service (12b-1) Fees		None
Other Expenses		0.08%
Administration Fees	0.01%
Miscellaneous Other Expenses	0.07%
Total Annual Fund Operating Expenses		0.11%
Fee Waivers and/or Expense Reimbursements^2,3		—
Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements^2,3		0.11%

¹	The fees and expenses shown in the table above and the example that follows include both the expenses of the Fund and its share of the allocated expenses of Total International ex U.S. Index Master Portfolio (the “Master Portfolio”), a series of Master Investment Portfolio (“MIP”). The management fees are paid by the Master Portfolio.
²	As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 33, BlackRock Fund Advisors (“BFA”), the investment adviser for the Master Portfolio, has contractually agreed to waive the management fee with respect to any portion of the Master Portfolio’s assets estimated to be attributable to investments in other equity and fixed-income mutual funds and exchange-traded funds managed by BFA or its affiliates that have a contractual management fee, through April 30, 2019. The contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested trustees of MIP or by a vote of a majority of the outstanding voting securities of the Master Portfolio.
³	As described in the “Management of the Funds” section of the Fund’s prospectus beginning on page 33, BFA and BlackRock Advisors, LLC (“BAL”), the administrator for the Fund, have contractually agreed to waive and/or reimburse fees or expenses in order to limit Total Annual Fund Operating Expenses After Fee Waivers and/or Expense Reimbursements of the Fund (excluding Dividend Expense, Interest Expense, Acquired Fund Fees and Expenses and certain other Fund expenses) to 0.11% of average daily net assets for Class K Shares through April 30, 2019. The Fund may have to repay some of these waivers and reimbursements to BFA and BAL in the following two years. This contractual agreement may be terminated upon 90 days’ notice by a majority of the non-interested trustees of the Trust or of MIP, as applicable, or by a vote of a majority of the outstanding voting securities of the Fund or the Master Portfolio, as applicable.

Example:

This 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 and then redeem 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
Class K Shares	$11	$35	$62	$141

Portfolio Turnover:

The Master Portfolio 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 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 Master Portfolio’s portfolio turnover rate was 57% of the average value of its portfolio.

Principal Investment Strategies of the Fund

The Total International Index Fund employs a “passive” management approach, attempting to invest in a portfolio of assets whose performance is expected to match approximately the performance of the MSCI ACWI ex USA Index. The Fund will be substantially invested in equity securities in the MSCI ACWI ex USA Index, and will invest, under normal circumstances, at least 80% of its assets in securities or other financial instruments that are components of or have economic characteristics similar to the securities included in the MSCI ACWI ex USA Index. Equity securities consist primarily of common stock, preferred stock, securities convertible into common stock and securities or other instruments whose price is linked to the value of common stock.

The Fund will invest in the common stocks represented in the MSCI ACWI ex USA Index in roughly the same proportions as their weightings in the MSCI ACWI ex USA Index. The MSCI ACWI ex USA Index is a free float-adjusted market capitalization index designed to measure the combined equity market performance of developed and emerging market countries, excluding the United States. The component stocks have a market capitalization between $392 million and $288 billion as of April 17, 2018. The Fund may also engage in futures transactions. At times, the Fund may not invest in all of the common stocks in the MSCI ACWI ex USA Index, or in the same weightings as in the MSCI ACWI ex USA Index. At those times, the Fund chooses investments so that the market capitalizations, industry weightings and other fundamental characteristics of the stocks chosen are similar to the MSCI ACWI ex USA Index as a whole. The Fund may lend securities with a value up to 33¹⁄3% of its total assets to financial institutions that provide cash or securities issued or guaranteed by the U.S. Government as collateral. 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 MSCI ACWI ex USA Index is concentrated.

The Fund is a “feeder” fund that invests all of its assets in the Master Portfolio, which has the same investment objective and strategies as the Fund. All investments are made at the Master Portfolio level. This structure is sometimes called a “master/feeder” structure. The Fund’s investment results will correspond directly to the investment results of the Master Portfolio. For simplicity, this prospectus uses the name of the Fund or the term “Fund” (as applicable) to include the Master Portfolio.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Total International Index Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of the principal risks of investing in the Fund.

■	Concentration Risk — The Fund reserves the right to concentrate its investments (i.e., invest 25% or more of its total assets in securities of issuers in a particular industry) to approximately the same extent that the Underlying Index concentrates in a particular industry. To the extent the Fund concentrates in a particular industry, it may be more susceptible to economic conditions and risks affecting that industry.
■	Convertible Securities Risk — The market value of a convertible security performs like that of a regular debt security; that is, if market interest rates rise, the value of a convertible security usually falls. In addition, convertible securities are subject to the risk that the issuer will not be able to pay interest or dividends when due, and their market value may change based on changes in the issuer’s credit rating or the market’s perception of the issuer’s creditworthiness. Since it derives a portion of its value from the common stock into which it may be converted, a convertible security is also subject to the same types of market and issuer risks that apply to the underlying common stock.
■	Emerging Markets Risk — Emerging markets are riskier than more developed markets because they tend to develop unevenly and may never fully develop. Investments in emerging markets may be considered speculative. Emerging markets are more likely to experience hyperinflation and currency devaluations, which adversely affect returns to U.S. investors. In addition, many emerging securities markets have far lower trading volumes and less liquidity than developed markets.
■	Equity Securities Risk — Stock markets are volatile. The price of equity securities fluctuates based on changes in a company’s financial condition and overall market and economic conditions.
■	Foreign Securities Risk — Foreign investments often involve special risks not present in U.S. investments that can increase the chances that the Fund will lose money. These risks include:

■	The Fund generally holds its foreign securities and cash in foreign banks and securities depositories, which may be recently organized or new to the foreign custody business and may be subject to only limited or no regulatory oversight.
■	Changes in foreign currency exchange rates can affect the value of the Fund’s portfolio.
■	The economies of certain foreign markets may not compare favorably with the economy of the United States with respect to such issues as growth of gross national product, reinvestment of capital, resources and balance of payments position.
■	The governments of certain countries may prohibit or impose substantial restrictions on foreign investments in their capital markets or in certain industries.
■	Many foreign governments do not supervise and regulate stock exchanges, brokers and the sale of securities to the same extent as does the United States and may not have laws to protect investors that are comparable to U.S. securities laws.
■	Settlement and clearance procedures in certain foreign markets may result in delays in payment for or delivery of securities not typically associated with settlement and clearance of U.S. investments.
■	The European financial markets have recently experienced volatility and adverse trends due to concerns about economic downturns in, or rising government debt levels of, several European countries. These events may spread to other countries in Europe. These events may affect the value and liquidity of certain of the Fund’s investments.

■	Futures Risk — The Fund’s use of futures may reduce the Fund’s returns. In these transactions, the Fund is subject to liquidity risk and correlation risk (i.e., that fluctuations in a future’s value may not correlate with the change in market value of the instruments held by the Fund).
■	Index Fund Risk — An index fund has operating and other expenses while an index does not. As a result, while the Fund will attempt to track the MSCI ACWI ex USA Index as closely as possible, it will tend to underperform the index to some degree over time. If an index fund is properly correlated to its stated index, the fund will perform poorly when the index performs poorly.
■	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.
■	Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.
■	Mid Cap Securities Risk — The securities of mid cap companies generally trade in lower volumes and are generally subject to greater and less predictable price changes than the securities of larger capitalization companies.
■	Securities Lending Risk — Securities lending involves the risk that the borrower may fail to return the securities in a timely manner or at all. As a result, the Fund may lose money and there may be a delay in recovering the loaned securities. The Fund could also lose money if it does not recover the securities and/or the value of the collateral falls, including the value of investments made with cash collateral. These events could trigger adverse tax consequences for the Fund.
■	Small Cap and Emerging Growth Securities Risk — Small cap or emerging growth companies may have limited product lines or markets. They may be less financially secure than larger, more established companies. They may depend on a more limited management group than larger capitalized companies.
■	Tracking Error Risk — Tracking error 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, differences in transaction costs, the Fund’s holding of uninvested cash, differences in timing of the accrual of or the valuation of dividends or interest, tax gains or losses, 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.

Performance Information

The information shows you how the performance of Total International Index Fund has varied for the periods since inception and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the MSCI ACWI ex USA Index. To the extent that dividends and distributions have been paid by the Fund, the performance information for the Fund in the chart and table assumes reinvestment of the dividends and distributions. As with all such investments, past performance (before and after taxes) is not an indication of future results. The table includes all applicable fees. If BFA, BAL and their affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance, including its current net asset value, can be obtained by visiting http://www.blackrock.com or can be obtained by phone at (800) 882-0052.

Class K Shares

ANNUAL TOTAL RETURNS

iShares MSCI Total International Index Fund
As of 12/31

During the periods shown in the bar chart, the highest return for a quarter was 11.47% (quarter ended March 31, 2012) and the lowest return for a quarter was -11.94% (quarter ended September 30, 2015).

As of 12/31/17 Average Annual Total Returns	1 Year	5 Years	Since Inception (June 30, 2011)
iShares MSCI Total International Index Fund — Class K Shares
Return Before Taxes	27.62%	6.35%	4.47%
Return After Taxes on Distributions	26.94%	5.15%	3.47%
Return After Taxes on Distributions and Sale of Fund Shares	16.44%	4.83%	3.44%
MSCI ACWI ex USA Index (Reflects no deduction for fees, expenses or taxes)	27.19%	6.80%	4.72%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

Investment Adviser

The Master Portfolio’s investment adviser is BlackRock Fund Advisors (previously defined as “BFA”).

Portfolio Managers

Name	Portfolio Manager of the Master Portfolio Since	Title
Alan Mason	2014	Managing Director of BlackRock, Inc.
Greg Savage, CFA	2012	Managing Director of BlackRock, Inc.
Jennifer Hsui, CFA	2016	Managing Director of BlackRock, Inc.
Creighton Jue, CFA	2016	Managing Director of BlackRock, Inc.
Rachel Aguirre	2016	Managing Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

Class K Shares of the Fund are available only to (i) certain employee benefit plans, such as health savings accounts, and certain employer-sponsored retirement plans (not including SEP IRAs, SIMPLE IRAs and SARSEPs) (collectively, “Employer-Sponsored Retirement Plans”), (ii) collective trust funds, investment companies and other pooled investment vehicles, each of which may purchase shares of the Fund through a Financial Intermediary (as defined below) that has entered into an agreement with the Fund’s distributor to purchase such shares, (iii) “Institutional Investors,” which include, but are not limited to, endowments, foundations, family offices, banks and bank trusts, local, city, and state governmental institutions, corporations and insurance company separate accounts, each of which may purchase shares of the Fund through a Financial Intermediary that has entered into an agreement with the Fund’s distributor to purchase such shares, (iv) fee-based advisory platforms of a Financial Intermediary that (a) has specifically acknowledged in a written agreement with the Fund’s distributor and/or its affiliate(s) that the Financial Intermediary shall offer such shares to fee-based advisory clients through an omnibus account held at the Fund or (b) transacts in the Fund’s shares through another intermediary that has executed such an agreement and (v) any other investors who met the eligibility criteria for BlackRock Shares or Class K Shares prior to August 15, 2016 and have continually held Class K Shares of the Fund in the same account since August 15, 2016.

You may purchase or redeem shares of the Fund each day the New York Stock Exchange is open. Purchase orders may also be placed by calling (800) 537-4942, by mail (c/o BlackRock, P.O. Box 9819, Providence, Rhode Island 02940-8019), or online at www.blackrock.com. Institutional Investors are subject to a $5 million minimum initial investment requirement. Other investors, including Employer-Sponsored Retirement Plans, have no minimum initial investment requirement. There is no minimum investment amount for additional purchases.

Tax Information

Different income tax rules apply depending on whether you are invested through a qualified tax-exempt plan described in section 401(a) of the Internal Revenue Code of 1986, as amended. If you are invested through such a plan (and Fund shares are not “debt-financed property” to the plan), then the dividends paid by the Fund and the gain realized from a redemption or exchange of Fund shares will generally not be subject to U.S. federal income taxes until you withdraw or receive distributions from the plan. If you are not invested through such a plan, then the Fund’s dividends and gain from a redemption or exchange may be subject to U.S. federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor.

Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a financial professional or selected securities dealer, broker, investment adviser, service provider or industry professional (including BlackRock, The PNC Financial Services Group, Inc. and their respective affiliates) (each a “Financial Intermediary”), the Fund and BlackRock Investments, LLC, the Fund’s distributor, or its affiliates may pay the Financial Intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the Financial Intermediary and your individual financial professional to recommend the Fund over another investment.

Class K Shares are only available through a Financial Intermediary if the Financial Intermediary will not receive from Fund assets, or the Fund’s distributor’s or an affiliate’s resources, any commission payments, shareholder servicing fees (including sub-transfer agent and networking fees), or distribution fees (including Rule 12b-1 fees) with respect to assets invested in Class K Shares. Ask your individual financial professional or visit your Financial Intermediary’s website for more information.

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INVESTMENT COMPANY ACT FILE # 811-07332

SPRO-TI-K-0418