# EDGAR Filing Document

**Accession Number:** 0000822632
**File Stem:** 0001193125-26-198379
**Filing Date:** 2026-5
**Character Count:** 20110
**Document Hash:** c60b947172eb8ee39371d586406e5310
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-198379.hdr.sgml**: 20260501

**ACCESSION NUMBER**: 0001193125-26-198379

**CONFORMED SUBMISSION TYPE**: 497K

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20260501

**DATE AS OF CHANGE**: 20260430

**EFFECTIVENESS DATE**: 20260501

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** WILLIAM BLAIR FUNDS
- **CENTRAL INDEX KEY:** 0000822632

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 497K
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 033-17463
- **FILM NUMBER:** 26928207

**BUSINESS ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606
- **BUSINESS PHONE:** 3123648000

**MAIL ADDRESS:**
- **STREET 1:** 150 NORTH RIVERSIDE PLAZA
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60606

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** WILLIAM BLAIR MUTUAL FUNDS INC
- **DATE OF NAME CHANGE:** 19960112

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** BLAIR WILLIAM READY RESERVES INC
- **DATE OF NAME CHANGE:** 19920316

## Series and Classes Contracts Data

### William Blair Institutional International Growth Fund (Series ID: S000008605)

| Class ID   | Class Name          | Ticker Symbol   |
|:---|:---|:---|
| C000023546 | Institutional Class | WBIIX           |

Summary Prospectus May 1, 2026

![LOGO](g18047logo_01.jpg)

Institutional International Growth Fund

Institutional WBIIX

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, Statement of Additional Information and other information about the Fund online at https://www.williamblairfunds.com/literature/forms/. You can also get this information at no cost by calling 1-800-742-7272 or by sending an e-mail request to fundinfo@williamblair.com. The Fund's Prospectus and Statement of Additional Information, each dated May 1, 2026, as supplemented, are incorporated by reference into this Summary Prospectus.

**INVESTMENT OBJECTIVE:** The William Blair Institutional International Growth Fund seeks long-term capital appreciation.

**FEES AND EXPENSES:** This table describes the fees and expenses that you may pay if you buy, hold and sell 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)**:**

Maximum Sales Charge (Load) Imposed on Purchases None <br> Redemption Fee None

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

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| | |
|:---|:---|
|  Management Fee\* | 0.85% |
|  Distribution (Rule 12b-1) Fee |  |
|  Other Expenses | 0.06% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total Annual Fund Operating Expenses | 0.91% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Fee Waiver and/or Expense Reimbursement\*\* | 0.06% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement\*\*\* | 0.85% |

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\* The Management Fee has been restated to reflect a reduction to 0.85% of average daily net assets effective May 1, 2025. 

\*\* William Blair Investment Management, LLC (the "Adviser") has entered into a contractual agreement with the Fund to waive fees and/or reimburse expenses in order to limit the Fund's operating expenses (excluding interest expenses, taxes, brokerage commissions, acquired fund fees and expenses, dividend and interest expenses on short sales, other investment-related costs and extraordinary expenses, such as litigation and other expenses not incurred in the ordinary course of the Fund's business) to 0.85% of average daily net assets for shares until April 30, 2027. The Adviser may not terminate this arrangement prior to April 30, 2027 without the approval of the Fund's Board of Trustees. 

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\*\*\* The Total Annual Fund Operating Expenses After Fee Waiver and/or Expense Reimbursement does not equal the net expense ratio to average daily net assets in the Financial Highlights section of this prospectus as a result of a change in the management fee and contractual expense limits. 

**Example:** This example is intended to help you compare the cost of investing in shares of 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 the Fund's operating expenses remain the same. The figures reflect the expense limitation for the first year. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

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| | | | |
|:---|:---|:---|:---|
| **1 Year** | **3 Years** | **5 Years** | **10 Years** |
| $87 | $284 | $498 | $1114 |

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**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 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 79% of the average value of its portfolio.

**PRINCIPAL INVESTMENT STRATEGIES:** Under normal market conditions, the Fund invests at least 80% of its total assets in a diversified portfolio of equity securities, including common stocks and other forms of equity investments (e.g., securities convertible into common stocks), issued by companies of all sizes domiciled outside the U.S. that the Adviser believes have above-average growth, profitability and quality characteristics. The Adviser seeks investment opportunities in companies at different stages of development ranging from large, well-established companies to smaller companies at earlier stages of development. The Fund's investments are normally allocated among at least six different countries and no more than 50% of the Fund's equity holdings may be invested in securities of issuers in one country at any given time. Normally, the Fund's investments will be divided among Continental Europe, the United Kingdom, Canada, Japan and the markets of the Pacific Basin. The Fund may invest the greater of 35% of its net assets or twice the emerging markets component of the MSCI All Country World ex USA Investable Market Index ("ACWI ex USA IMI") (net) in emerging markets, which include every country in the world except the United States, Canada, Japan, Australia, New Zealand, Hong Kong, Singapore and most Western European countries.

In choosing investments, the Adviser performs fundamental company analysis and focuses on stock selection. The Adviser generally seeks equity securities, including common stocks, of companies that historically have had superior growth, profitability and quality relative to local markets and relative to companies within the same industry worldwide, and that are expected to continue such performance. Such companies generally will exhibit superior business fundamentals, including leadership in their field, quality products or services, distinctive marketing and distribution, pricing flexibility and revenue from products or services consumed on a steady, recurring basis. These business characteristics should be accompanied by management that is shareholder return-oriented and that uses conservative accounting policies. Companies with above-average returns on equity, strong balance sheets and consistent, above-average earnings growth will be the primary focus. Stock selection will take into account both local and global comparisons.

The Adviser will vary the Fund's sector and geographic diversification based upon the Adviser's ongoing evaluation of economic, market and political trends throughout the world. In making decisions regarding country allocation, the Adviser will consider such factors as the conditions and growth potential of various economies and securities markets, currency exchange rates, technological developments in the various countries and other pertinent financial, social, national and political factors.

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**PRINCIPAL RISKS:** The Fund's returns will vary, and you could lose money by investing in the Fund. The following is a summary of the principal risks associated with an investment in the Fund.

**Equity Funds General Risk.** The value of equity securities the Fund holds might decrease in response to the activities of an individual company or in response to general market, business and economic conditions. If this occurs, the Fund's share price may also decrease. In addition, there is the risk that individual securities may not perform as expected or a strategy used by the Adviser may fail to produce its intended result.

**Market Risk.** The value of the Fund's investments may go up or down, sometimes rapidly or unpredictably. The value of an investment may decline due to factors affecting securities markets generally or particular industries represented in the securities markets. The value of an investment may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, recessions, inflation, rapid interest rate changes, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. Local, regional or global events such as war, military conflict, geopolitical disputes, acts of terrorism, social unrest, tariffs and other restrictions on trade, sanctions, supply chain disruptions, increased government spending, natural disasters, the spread of infectious illness or other public health issues, or the threat or potential threat of one or more such events and developments could also significantly impact the Fund and its investments. The value of an investment may also decline due to factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within an industry. During a general downturn in the securities markets, multiple asset classes may decline in value simultaneously. Geopolitical and other events may also disrupt securities markets and adversely affect global economies and markets and thereby decrease the value of the Fund's investments.

**Foreign Investment Risk.** The risks of foreign investments may include less publicly available information, less stringent investor protections and disclosure standards, less governmental regulation and supervision of foreign stock exchanges, brokers and issuers, share registration and custody, a lack of uniform accounting, auditing and financial reporting standards, practices and requirements, the possibility of expropriation, seizure or nationalization, confiscatory taxation, limits on repatriation, adverse changes in investment or exchange control regulations, political instability, restrictions on the flow of international capital, imposition of foreign withholding or other taxes, fluctuating currencies, inflation, difficulty in obtaining and enforcing judgments against foreign entities or other adverse political, social or diplomatic developments that could affect the Fund's investments. Foreign investments may be less liquid and their prices more volatile than the securities of U.S. companies. The Fund is expected to incur operating expenses that are higher than those of mutual funds investing exclusively in U.S. equity securities due to the higher custodial fees associated with foreign securities investments.

**Currency Risk.** The value of the Fund's portfolio may be affected by changes in exchange rates or control regulations. Currency exchange rates may fluctuate significantly over short periods of time for a number of reasons, including changes in interest rates. If a local currency gains against the U.S. dollar, the value of the security increases in U.S. dollar terms. If a local currency declines against the U.S. dollar, the value of the security decreases in U.S. dollar terms.

**Emerging Markets Risk.** Foreign investment risk is typically magnified in emerging markets, which are the less developed and developing nations.

**Geographic Risk.** To the extent that the Fund invests a significant portion of its assets in any one country or geographic region, the Fund will be subject to greater risk of loss or volatility than if the Fund always maintained wide geographic diversity among the countries and geographic regions in which it

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invests. Investing in any one country or geographic region makes the Fund more vulnerable to the risks of adverse securities markets, exchange rates and social, political, regulatory and economic events in that one country or geographic region.

**Smaller Company Risk.** Stocks of smaller companies involve greater risk than those of larger, more established companies. This is because smaller companies may be in earlier stages of development, may be dependent on a small number of products or services, may lack substantial capital reserves and/or do not have proven track records. Smaller companies may be traded in low volumes. This can increase volatility and increase the risk that the Fund will not be able to sell a security on short notice at a reasonable price. The securities of smaller companies may be more volatile and less liquid than securities of large capitalized companies.

**Share Ownership Concentration Risk.** To the extent that a significant portion of the Fund's shares is held by a limited number of shareholders or their affiliates, there is a risk that the share trading activities of these shareholders could disrupt the Fund's investment strategies, which could have adverse consequences for the Fund and other shareholders (e.g., by requiring the Fund to sell investments at inopportune times or causing the Fund to maintain larger-than-expected cash positions pending acquisition of investments).

**Style Risk.** Different investment styles (e.g., growth vs. value, quality bias, market capitalization focus) tend to shift in and out of favor depending on market conditions and investor sentiment, and at times when the growth investment style used by the Adviser for the Fund is out of favor, the Fund may underperform other equity funds that use different investment styles.

**Focus Risk.** To the extent that the Fund focuses its investments in particular industries, asset classes or sectors of the economy, any market changes affecting companies in those industries, asset classes or sectors may impact the Fund's performance.

**Operational and Technology Risk.** Cyber-attacks, disruptions, or failures that affect the Fund's service providers, counterparties, market participants, or issuers of securities held by the Fund may adversely affect the Fund and its shareholders, including by causing losses for the Fund or impairing Fund operations.

The Fund is not intended to be a complete investment program. The Fund is designed for long-term investors.

**The Fund involves a high level of risk and may not be appropriate for everyone.** You should only consider it for the aggressive portion of your portfolio.

**FUND PERFORMANCE HISTORY:** The information below provides some indication of the risks of investing in the Fund by showing changes in the Fund's performance from year to year and by showing how the Fund's average annual total returns for the periods indicated compare with those of a broad measure of market performance that is generally representative of the market sectors or types of investments in which the Fund invests. The Fund's past performance (before and after taxes) does not necessarily indicate how it will perform in the future. For more recent performance information, go to https://im.williamblair.com/investments/mutual-funds or call 1-800-635-2886.

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**Annual Total Returns.** The bar chart below provides an illustration of how the Fund's performance has varied in each of the last ten calendar years.

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| | | |
|:---|:---|:---|
| ![LOGO](g18047g96m02.jpg) | **Highest Quarterly**<br> **Return**<br> 25.41% (2Q20) | **Lowest Quarterly**<br> **Return**<br> (19.71)% (1Q20) |

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**Average Annual Total Returns** (For the periods ended December 31, 2025)**.** The table below shows returns on a before-tax and after-tax basis. 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. In some instances, the "Return After Taxes on Distributions and Sale of Fund Shares" may be greater than the "Return Before Taxes" because the investor is assumed to be able to use the capital loss on the sale of Fund shares to offset other taxable capital gains. Actual after-tax returns depend on an investor's tax situation and may differ from those shown. After-tax returns are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts.

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| | | | |
|:---|:---|:---|:---|
|  | **1 Year** | **5 Years** | **10 Years** |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Return Before Taxes | 18.05% | 1.78% | 7.03% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Return After Taxes on Distributions | 14.86% | (0.26)% | 5.24% |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Return After Taxes on Distributions and Sale of Fund Shares | 12.87% | 1.20% | 5.42% |
|  ***MSCI ACWI ex USA IMI (net)*** (reflects no deduction for fees, expenses or taxes) | 31.96% | 7.77% | 8.37% |

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**MANAGEMENT:** 

**Investment Adviser.** William Blair Investment Management, LLC is the investment adviser of the Fund.

**Portfolio Managers.** Simon Fennell and Andrew Siepker, Partners of the Adviser, co-manage the Fund. Mr. Fennell has co-managed the Fund since 2013. Mr. Siepker has co-managed the Fund since 2022.

**PURCHASE AND SALE OF FUND SHARES:** 

**Purchase.** The minimum initial investment is $5 million. There is no minimum for subsequent purchases. The Distributor reserves the right to offer shares without regard to the minimum purchase amount requirements to qualified or non-qualified employee benefit plans when an unaffiliated third party provides administrative and/or other support services to the plan. Certain exceptions to the minimum initial investment amount may apply. Shares are only available to certain investors. See "Your Account—Institutional Class Shares" for additional information on eligibility requirements applicable to purchasing shares.

**Sale.** Shares of the Fund are redeemable on any day the New York Stock Exchange is open for business by mail, wire or telephone, depending on the elections you make in the account application.

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**TAX INFORMATION:** The Fund intends to make distributions that may be taxed as ordinary income or capital gains, unless you are investing through a tax-advantaged investment plan. If you are investing through a tax-advantaged investment plan, withdrawals from the tax-advantaged investment plan may be subject to taxes.

**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), the Fund and its related companies may pay the intermediary for the sale of shares and related services. 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.