0000063091 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002037Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002042Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002043Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002044Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002046Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002048Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002049Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000002038Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:C000113374Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:PrincipalRisksMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member rr:RiskLoseMoneyMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member rr:RiskNotInsuredMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:InvestmentSelectionRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:EquityMarketRiskCompanyRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:ForeignRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:FocusRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:LiquidityRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:LargeShareholderRiskMember 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member rr:AfterTaxesOnDistributionsMember cik0000063091:C000002037Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member rr:AfterTaxesOnDistributionsAndSalesMember cik0000063091:C000002037Member 2024-12-31 2024-12-31 0000063091 cik0000063091:S000000696Member cik0000063091:StandardPoors500StockIndex1Member 2024-12-31 2024-12-31 iso4217:USD pure utr:Y N-1A MASSACHUSETTS INVESTORS TRUST 2025-04-30 2025-04-30 Massachusetts Investors Trust Summary of Key Information MITTX MITBX MITCX MITIX MITGX MIRTX MITHX MITDX MITJX Investment Objective The fund’s investment objective is to seek capital appreciation. Fees and Expenses This table describes the fees and expenses that you may pay when you buy, hold, and sell shares of the fund. Investors may also pay commissions or other fees to their financial intermediaries when they buy, hold, and sell shares of the fund, which are not reflected below. You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. More information about these and other waivers and reductions is available from your financial intermediary and in “Sales Charges and Waivers and Reductions” on page 9 and “Appendix A – Waivers and Reductions of Sales Charges” on page A-1 of the fund’s prospectus. You may qualify for sales charge reductions if, with respect to Class A shares, you and certain members of your family invest, or agree to invest in the future, at least $50,000 in MFS funds. 50000 Shareholder Fees (fees paid directly from your investment): 0.0575 0 0 0 0 0 0 0 0 0.0100 0.0400 0.0100 0 0 0 0 0 0 Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment): 0.0033 0.0033 0.0033 0.0033 0.0033 0.0033 0.0033 0.0033 0.0033 0.0025 0.0100 0.0100 0 0.0100 0.0050 0.0025 0 0 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0012 0.0005 0.0070 0.0145 0.0145 0.0045 0.0145 0.0095 0.0070 0.0045 0.0038 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 you redeem your shares at the end of the time periods (unless otherwise indicated); your investment has a 5% return each year; and the fund’s operating expenses remain the same. Although your actual costs will likely be higher or lower, under these assumptions your costs would be: 642 786 942 1395 548 759 992 1531 148 459 792 1531 248 459 792 1531 148 459 792 1531 46 144 252 567 148 459 792 1735 97 303 526 1166 72 224 390 871 46 144 252 567 39 122 213 480 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 shares are held in a taxable account. These transaction 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 25% of the average value of its portfolio. 0.25 Principal Investment Strategies MFS (Massachusetts Financial Services Company, the fund's investment adviser) normally invests the fund’s assets primarily in equity securities. Equity securities include common stocks, depositary receipts, and other securities that represent an ownership interest (or right to acquire an ownership interest) in a company or other issuer.In selecting investments for the fund, MFS is not constrained by any particular investment style. MFS may invest the fund’s assets in the stocks of companies it believes to have above average earnings growth potential compared to other companies (growth companies), in the stocks of companies it believes are undervalued compared to their perceived worth (value companies), or in a combination of growth and value companies. While MFS may invest the fund’s assets in securities of companies of any size, MFS primarily invests in securities of companies with large capitalizations.MFS may invest the fund’s assets in foreign securities. MFS normally invests the fund's assets across different industries and sectors, but MFS may invest a significant percentage of the fund's assets in issuers in a single industry or sector.MFS uses an active bottom-up investment approach to buying and selling investments for the fund. Investments are selected primarily based on fundamental analysis of individual issuers. Quantitative screening tools that systematically evaluate issuers may also be considered. Principal Risks As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency.The principal risks of investing in the fund are: Principal Risks As with any mutual fund, the fund may not achieve its objective and/or you could lose money on your investment in the fund. An investment in the fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other governmental agency. Investment Selection Risk: MFS' investment analysis and its selection of investments may not produce the intended results and/or can lead to an investment focus that results in the fund underperforming other funds with similar investment strategies and/or underperforming the markets in which the fund invests. In addition, to the extent MFS considers quantitative tools in managing the fund, such tools may not produce the intended results. Equity Market Risk/Company Risk: Equity markets are volatile and can decline significantly in response to changes in, or investor perceptions of, issuer, market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These conditions can affect a single issuer or type of security, issuers within a broad market sector, industry or geographic region, or the equity markets in general. Certain events can have a dramatic adverse effect on equity markets and may lead to periods of high volatility in an equity market or a segment of an equity market. The value of an investment held by the fund may decline due to factors directly related to the issuer. Foreign Risk: Exposure to foreign markets through issuers or currencies can involve additional risks relating to market, economic, industry, political, regulatory, geopolitical, environmental, public health, and other conditions. These factors can make foreign investments, especially those tied economically to countries with developing economies or countries subject to sanctions or the threat of new or modified sanctions, more volatile and less liquid than U.S. investments. In addition, foreign markets can react differently to these conditions than the U.S. market. Focus Risk: Issuers in a single industry, sector, country, or region can react similarly to market, currency, political, economic, regulatory, geopolitical, environmental, public health, and other conditions, and the fund's performance will be affected by the conditions in the industries, sectors, countries, and regions to which the fund is exposed. Liquidity Risk: It may be difficult to value, and it may not be possible to sell, certain investments, types of investments, and/or investments in certain segments of the market, and the fund may have to sell certain of these investments at prices or times that are not advantageous in order to meet redemptions or other cash needs. Large Shareholder Risk: From time to time, shareholders of the fund (which may include institutional investors, financial intermediaries, or other MFS funds) may make relatively large redemptions or purchases of fund shares. These transactions may cause the fund to sell securities or invest additional cash, as the case may be, at disadvantageous prices. Redemptions of a large number of shares also may increase transaction and other costs or have adverse tax consequences for shareholders of the fund by requiring a sale of portfolio securities. Purchases of a large number of shares may adversely affect the fund's performance to the extent that it takes time to invest new cash and the fund maintains a larger cash position than it ordinarily would. Performance Information The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance.The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. Updated performance is available online at mfs.com or by calling 1-800-225-2606. The bar chart and performance table below are intended to provide some indication of the risks of investing in the fund by showing changes in the fund’s performance over time and how the fund’s performance over time compares with that of a broad measure of market performance. The fund’s past performance (before and after taxes) does not necessarily indicate how the fund will perform in the future. mfs.com 1-800-225-2606 Class A Bar Chart. The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown. The bar chart does not take into account any sales charges (loads) that you may be required to pay upon purchase or redemption of the fund’s shares. If these sales charges were included, they would reduce the returns shown. The total return for the three-month period ended March 31, 2025, was (2.54)%. During the period(s) shown in the bar chart, the highest quarterly return was 19.45% (for the calendar quarter ended June 30, 2020) and the lowest quarterly return was (20.43)% (for the calendar quarter ended March 31, 2020). The total return for the three-month period ended 2025-03-31 highest quarterly return 0.1945 2020-06-30 lowest quarterly return -0.2043 2020-03-31 Performance Table. Average Annual Total Returns (For the Periods Ended December 31, 2024) Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes Returns Before Taxes 0.1477 0.1044 0.1059 0.1775 0.1071 0.1058 0.1996 0.1182 0.1152 0.1878 0.1070 0.1041 0.1935 0.1126 0.1097 0.1964 0.1154 0.1125 0.1998 0.1182 0.1152 0.2005 0.1191 0.1162 0.1280 0.1023 0.1060 Returns After Taxes on Distributions 0.0935 0.0792 0.0845 Returns After Taxes on Distributions and Sale of Fund Shares 0.0999 0.0781 0.0816 Reflects no deduction for fees, expenses, or taxes Standard & Poor's 500 Stock Index 0.2502 0.1453 0.1310 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. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (IRAs). The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown. 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. Your actual after-tax returns will depend on your own tax situation, and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans or individual retirement accounts (IRAs). The after-tax returns are shown for only one of the fund’s classes of shares, and after-tax returns for the fund’s other classes of shares will vary from the returns shown. 485BPOS 2025-04-30 2024-12-31 0000063091 2025-04-29 false ~ http://www.MFS.com/20241231/role/RRSchedule4 ~ ~ http://www.MFS.com/20241231/role/RRSchedule5 ~ ~ http://www.MFS.com/20241231/role/RRSchedule6 ~ ~ http://www.MFS.com/20241231/role/RRSchedule7 ~ ~ http://www.MFS.com/20241231/role/RRBarChart8 ~ ~ http://www.MFS.com/20241231/role/RRSchedule9 ~ 0.0028 0.0877 0.2356 -0.0531 0.3191 0.1412 0.2682 -0.1634 0.1915 0.1968 This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase. ~ http://www.MFS.com/20241231/role/RRSchedule10 ~ This contingent deferred sales charge (CDSC) applies to shares purchased without an initial sales charge and redeemed within 18 months of purchase. Shares automatically convert to Class A shares approximately eight years after purchase; therefore, the expense examples reflect Class A share expenses after eight years.