Summary Prospectus by Investment Company (Form 497K)

April 28, 2026

Summary Prospectus

Vanguard Institutional Total Stock Market Index Fund

Institutional Shares & Institutional Plus Shares

Vanguard Institutional Total Stock Market Index Fund Institutional Shares (VITNX)
Vanguard Institutional Total Stock Market Index Fund Institutional Plus Shares (VITPX)

The Fund's statutory Prospectus and Statement of Additional Information dated April 28, 2026, as may be amended or supplemented, are incorporated into and made part of this Summary Prospectus by reference.

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 and other information about the Fund online at www.vanguard.com/prospectus and https://personal.vanguard.com/us/literature/reports/MFs. You can also obtain this information at no cost by calling 800-662-7447 (if you are an individual investor) or 800-523-1036 (if you are a client of Vanguard's Institutional Division) or by sending an email request to [email protected].

 

The Securities and Exchange Commission (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.

Investment Objective

Vanguard Institutional Total Stock Market Index Fund (the "Fund") seeks to track the performance of a benchmark index that measures the investment return of the overall stock market.

Fees and Expenses

The following tables describe the fees and expenses you may pay if you buy, hold, and sell Institutional Shares or Institutional Plus Shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the tables and examples below.

Shareholder Fees
(Fees paid directly from your investment) 

	Institutional Shares	Institutional Plus Shares
Sales Charge (Load) Imposed on Purchases	None	None
Purchase Fee	None	None
Sales Charge (Load) Imposed on Reinvested Dividends	None	None
Redemption Fee	None	None

Annual Fund Operating Expenses
(Expenses that you pay each year as a percentage of the value of your investment) 

	Institutional Shares	Institutional Plus Shares
Management Fees	0.02 %	0.02%
12b-1 Distribution Fee	None	None
Other Expenses	0.01 %	0.00%
Total Annual Fund Operating Expenses	0.03 %	0.02%

Examples

These examples are intended to help you compare the cost of investing in the Fund with the cost of investing in other funds. The examples assume 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 examples also assume that your investment has a 5% return each year and that the Fund's operating expenses remain the same. 

	1 Year	3 Years	5 Years	10 Years
Institutional Shares	$3	$10	$17	$39
Institutional Plus Shares	$2	$6	$11	$26

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 examples, affect the Fund's performance. During the most recent fiscal year, the Fund's portfolio turnover rate was 5% of the average value of its portfolio.

Principal Investment Strategies

The Fund employs an indexing investment approach designed to track the performance of the CRSP US Total Market Index (the "Target Index"), which represents approximately 100% of the investable U.S. stock market, as determined by the index provider. The Target Index includes large-, mid-, small-, and micro-cap stocks regularly traded on the New York Stock Exchange and Nasdaq. Under normal circumstances, the Fund invests at least 80% of its net assets, plus the amount of any borrowings for investment purposes, in the stocks that make up the Target Index. The Fund invests by sampling the Target Index, meaning that it holds a range of securities that, in the aggregate, approximates the full Target Index in terms of key risk factors and other characteristics.

The Fund may become nondiversified, as defined under the Investment Company Act of 1940, solely as a result of tracking an index. This could occur due to events such as an index rebalance or market movement. A nondiversified fund it may invest in a greater percentage of its assets in the securities of particular issuers as compared with diversified funds. In addition, the Fund could become concentrated in an industry or group of industries if the Target Index becomes concentrated due to market conditions or the performance of a single or related group of issuers.

Principal Risks

As with any investment, an investment in the Fund could lose money over any time period. The Fund's share price and total return may fluctuate, potentially within a wide range. The principal risks of investing in the Fund are summarized below. Each of the following risks could affect the Fund's performance:

• General Market Risk. The markets in which the Fund invests can be affected by a variety of factors. These factors, which can be real or perceived, may include economic, market, political, and regulatory conditions and developments as well as local, regional, or global events such as wars, military conflicts, natural disasters, and public health issues. In addition, investor sentiment and expectations regarding these factors can also impact the markets. Different parts of the market, including different industries and sectors as well as different types of securities, may react differently to factors that affect the market. These factors can contribute to market uncertainty, market volatility, and fluctuations in the value of the Fund's investments, thereby resulting in potential losses to the Fund over short or long periods.

• Investing in Equity Markets. The Fund invests in the equity markets. Equity markets have historically been cyclical, having periods of time when stock values rise and fall. Market volatility can lead to significant fluctuations in stock values, resulting in potential losses to the Fund.

• Market Capitalization (Market Cap). Companies are generally classified into three types of market cap depending on their size: small-, mid-, and large-cap. Companies can be further classified into micro- or mega-cap. Different factors can affect each market cap uniquely, and historically small- and mid-cap stocks have typically been more volatile due to the effects of changing economic conditions. Large companies may not reach the same levels of growth or performance as smaller companies, and they may be slower to react to competitive challenges. The performance of funds that invest in a subset of market caps could diverge from the performance of a fund that is focused on a broader representation of the stock market.

• Index Investing. The Fund is subject to risks associated with index investing. Because the Fund generally seeks to track the performance of the Target Index regardless of how the Target Index is performing, the Fund's performance may be lower than it would be if it were actively managed. Additionally, because the Fund does not hold all of the securities included in the Target Index, it is subject to the risk that the representative sample of securities selected by the advisor will, in the aggregate, vary from the investment profile of the full Target Index. The performance of the Fund's investments, in the aggregate, may not match the investment performance of the Target Index. This risk, known as tracking error risk, may be heightened during times of increased market volatility or under other unusual market conditions. The Fund also could be negatively impacted by changes to the Target Index made by the index provider or by errors made by the index provider. Any gains, losses, or costs associated with or resulting from an error

made by the index provider will generally be borne by the Fund and, as a result, the Fund's shareholders.

• Management of Certain Similar Funds. The name, investment objective, principal investment strategies, and risks of the Fund are similar to another separate fund managed by the Fund's portfolio managers. However, the investment results of the Fund may be higher or lower than, and there is no guarantee that the investment results of the Fund will be comparable to, that other fund.

• Nondiversification. By tracking its broad-based Target Index, the Fund could become nondiversified, as defined under the Investment Company Act of 1940, due to events such as an index rebalance or market movement. The performance of nondiversified funds may be negatively impacted by relatively few securities or even a single security and their shares may experience significant fluctuations in value.

• Concentration Risk. Except as may be necessary to approximate the composition of its Target Index, the Fund will not concentrate its investments in the securities of issuers whose principal business activities are in the same industry or group of industries. If the Target Index becomes concentrated and the Fund needs to concentrate in the same industry or group of industries, its performance could be negatively impacted by the industry or industries in which it is concentrated.

• Information Technology Sector. As of the Fund's most recent fiscal year end, stocks of companies within the information technology sector made up a significant portion of the Target Index. As a result, the performance of the Target Index, and therefore the performance of the Fund, may be impacted by the general condition of the information technology sector.

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

Annual Total Returns

The following bar chart and table show the Fund's historical performance and are intended to help you understand the risks of investing in the Fund. The bar chart shows how the performance of the Fund's Institutional Shares has varied from one calendar year to another over the periods shown. The table shows how the average annual total returns of the share classes presented compare with those of a broad-based securities market index and one or more additional indexes with similar investment characteristics of the Fund. Keep in mind that the Fund's past performance (before and after taxes) does not indicate how the Fund will perform in the future. Updated performance information is available on our website at vanguard.com/performance.

Annual Total Returns - Vanguard Institutional Total Stock Market Index Fund Institutional Shares   

During the periods shown in the bar chart, the highest and lowest returns for a calendar quarter were: 

	Total Return	Quarter
Highest	22.11 %	June 30, 2020
Lowest	-20.89 %	March 31, 2020

Average Annual Total Returns for Periods Ended December 31, 2025 

	1 Year	5 Years	10 Years
Vanguard Institutional Total Stock Market Index Fund Institutional Shares
Return Before Taxes	17.15 %	13.10 %	14.27 %
Return After Taxes on Distributions	16.33	12.03	13.21
Return After Taxes on Distributions and Sale of Fund Shares	10.59	10.21	11.62
Vanguard Institutional Total Stock Market Index Fund Institutional Plus Shares
Return Before Taxes	17.16 %	13.10 %	14.27 %
CRSP US Total Market Index (reflects no deduction for fees, expenses, or taxes)	17.15 %	13.08 %	14.25 %
Dow Jones U.S. Total Stock Market Float Adjusted Index (reflects no deduction for fees, expenses, or taxes)	17.05	13.07	14.21

Actual after-tax returns depend on your tax situation and may differ from those shown in the preceding table. When after-tax returns are calculated, it is assumed that the shareholder was in the highest individual federal marginal income tax bracket at the time of each distribution of income or capital gains or upon redemption. State and local income taxes are not reflected in the calculations. Please note that after-tax returns are shown only for Institutional Shares and may differ for each share class. After-tax returns are not relevant for a shareholder who holds fund shares in a tax-deferred account, such as an individual retirement account or a 401(k) plan. Also, figures captioned Return