Summary Prospectus
March 31, 2017

Loomis Sayles Limited Term Government and Agency Fund

Ticker Symbol: Class A (NEFLX), Class C (NECLX), Class N (LGANX), Class T (LGATX) and Class Y (NELYX)

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 ngam.natixis.com/us/fund-documents. You can also get this information at no cost by calling 800-225-5478 or by sending an e-mail request to NatixisFunds@ngam.natixis.com. The Fund's Prospectus and Statement of Additional Information, each dated March 31, 2017, as may be revised or supplemented from time to time, are incorporated by reference into this Summary Prospectus.

Investment Goal

The Fund seeks high current return consistent with preservation of capital.

Fund Fees & Expenses

The following table describes the fees and expenses that you may pay if you buy and hold shares of the Fund. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in the Natixis Fund Complex. More information about these and other discounts is available from your financial professional and in the section "How Sales Charges Are Calculated" on page 85 of the Prospectus, in Appendix A to the Prospectus and on page 115 in the section "Reduced Sales Charges" of the Statement of Additional Information ("SAI").

Shareholder Fees

(fees paid directly from your investment)	Class A		Class C		Class N	Class T		Class Y
Maximum sales charge (load) imposed on purchases (as a percentage of offering price)	2.25	%	None		None	2.50	%	None
Maximum deferred sales charge (load) (as a percentage of original purchase price or redemption proceeds, as applicable)	None *		1.00	%	None	None		None
Redemption fees	None		None		None	None		None

*A 0.75% contingent deferred sales charge ("CDSC") may apply to certain purchases of Class A shares of $500,000 or more that are redeemed within eighteen months of the date of purchase.

Annual Fund Operating Expenses

(expenses that you pay each year as a percentage of the value of your investment)	Class A		Class C		Class N		Class T		Class Y
Management fees	0.36	%	0.36	%	0.36	%	0.36	%	0.36	%
Distribution and/or service (12b-1) fees	0.25	%	1.00	%	0.00	%	0.25	%	0.00	%
Other expenses	0.16	%	0.16	%	0.08	% 1	0.16	% 1	0.16	%
Total annual fund operating expenses	0.77	%	1.52	%	0.44	%	0.77	%	0.52	%
Fee waiver and/or expense reimbursement 2,3,4	0.00	%	0.00	%	0.00	%	0.00	%	0.00	%
Total annual fund operating expenses after fee waiver and/or expense reimbursement	0.77	%	1.52	%	0.44	%	0.77	%	0.52	%

1Other expenses are estimated for the current fiscal year.

2Loomis, Sayles & Company, L.P. ("Loomis Sayles" or the "Adviser") has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.80%, 1.55%, 0.50% and 0.55% of the Fund's average daily net assets for Class A, C, N and Y shares, respectively, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below the applicable expense limitations for Class A, C, N and Y shares. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

3NGAM Advisors has given a binding contractual undertaking to the Fund to reimburse any and all transfer agency expenses for Class N shares. This undertaking is in effect through January 31, 2018 and may be terminated before then only with the consent of the Fund's Board of Trustees.

4Loomis Sayles has given a binding contractual undertaking to the Fund to limit the amount of the Fund's total annual fund operating expenses to 0.80% of the Fund's average daily net assets for Class T shares, exclusive of brokerage expenses, interest expense, taxes, acquired fund fees and expenses, organizational and extraordinary expenses, such as litigation and indemnification expenses. This undertaking is in effect through January 31, 2019 and may be terminated before then only with the consent of the Fund's Board of Trustees. The Adviser will be permitted to recover, on a class by class basis, management fees waived and/or expenses reimbursed to the extent that expenses in later periods fall below the applicable expense limitation for Class T shares. The Fund will not be obligated to repay any such waived/reimbursed fees and expenses more than one year after the end of the fiscal year in which the fees or expenses were waived/reimbursed.

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Fund Summary

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 (except where indicated). 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:

If shares are redeemed:	1 year		3 years		5 years		10 years
Class A	$	302	$	465	$	643	$	1,158
Class C	$	255	$	480	$	829	$	1,813
Class N	$	45	$	141	$	246	$	555
Class T	$	327	$	490	$	667	$	1,180
Class Y	$	53	$	167	$	291	$	653

If shares are not redeemed:	1 year		3 years		5 years		10 years
Class C	$	155	$	480	$	829	$	1,813

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 for you if your 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 its most recently ended fiscal year, the Fund's portfolio turnover rate was 109% of the average value of its portfolio.

Investments, Risks and Performance

Principal Investment Strategies

Under normal market conditions, the Fund will invest at least 80% of its net assets (plus any borrowings made for investment purposes) in investments issued or guaranteed by the U.S. government, its agencies or instrumentalities.

The Adviser follows a total return-oriented investment approach in selecting securities for the Fund. It seeks securities that will provide the Fund with an average credit quality equal to the credit rating of the U.S. Government's long-term debt and an effective portfolio duration range of two to four years (although not all securities selected will have these characteristics and the Adviser may look for other characteristics if market conditions change). The Fund may invest in securities with credit quality above or below the credit rating of the U.S. Government's long-term debt. In determining credit quality, the Adviser will look to the highest credit rating assigned by S&P Global Ratings ("S&P"), Fitch Investor Services, Inc. ("Fitch") or Moody's Investors Service, Inc. ("Moody's").

In deciding which securities to buy and sell, the Adviser will consider, among other things, the financial strength of the issuer, current interest rates, current valuations, the Adviser's expectations regarding future changes in interest rates and comparisons of the level of risk associated with particular investments with the Adviser's expectations concerning the potential return of those investments.

In selecting investments for the Fund, the Adviser's research analysts work closely with the Fund's portfolio managers to develop an outlook on the economy from research produced by various financial firms and specific forecasting services or from economic data released by the U.S. and foreign governments as well as the Federal Reserve Bank. The analysts also conduct a thorough review of individual securities to identify what they consider attractive values in the U.S. government security marketplace through the use of quantitative tools such as internal and external computer systems and software. The Adviser continuously monitors an issuer's creditworthiness to assess whether the obligation remains an appropriate investment for the Fund. The Adviser seeks to balance opportunities for yield and price performance by combining macroeconomic analysis with individual security selection. It emphasizes securities that tend to perform particularly well in response to interest rate changes, such as U.S. Treasury securities in a declining interest rate environment and mortgage-backed or U.S. government agency securities in a steady or rising interest rate environment. The Adviser seeks to increase the opportunity for higher yields while maintaining the greater price stability that intermediate-term bonds have compared to bonds with longer maturities.

In connection with its principal investment strategies, the Fund may also invest in investment grade corporate notes and bonds, zero-coupon bonds, securities issued pursuant to Rule 144A under the Securities Act of 1933 ("Rule 144A securities"), asset-backed securities and mortgage-related securities including mortgage dollar rolls. Except as provided above or as required by applicable law, the Fund is not limited in the percentage of its assets that it may invest in these instruments.

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Fund Summary

Principal Investment Risks

The principal risks of investing in the Fund are summarized below. The Fund does not represent a complete investment program. You may lose money by investing in the Fund.

Agency Securities Risk: Agency securities are subject to fixed-income securities risk. Certain debt securities issued or guaranteed by agencies of the U.S. government are guaranteed as to the payment of principal and interest by the relevant entity but have not been backed by the full faith and credit of the U.S. government. Instead, they have been supported only by the discretionary authority of the U.S. government to purchase the agency's obligations. An event affecting the guaranteeing entity could adversely affect the payment of principal or interest or both on the security and, therefore, these types of securities should be considered to be riskier than U.S. government securities.

Credit Risk: Credit risk is the risk that the issuer or the guarantor of a fixed-income security will be unable or unwilling to make timely payments of interest or principal or to otherwise honor its obligations. 

Interest Rate Risk: Interest rate risk is the risk that the value of the Fund's investments will fall if interest rates rise.  Generally, the value of fixed-income securities rises when prevailing interest rates fall and falls when interest rates rise.  Interest rate risk generally is greater for funds that invest in fixed-income securities with relatively longer durations than for funds that invest in fixed-income securities with shorter durations. The value of zero-coupon securities and securities with longer maturities are generally more sensitive to fluctuations in interest rates than other fixed-income securities.  In addition, an economic downturn or period of rising interest rates could adversely affect the market for these securities and reduce the Fund's ability to sell them, negatively impacting the performance of the Fund.

Liquidity Risk:  Liquidity risk is the risk that the Fund may be unable to find a buyer for its investments when it seeks to sell them or to receive the price it expects. Decreases in the number of financial institutions willing to make markets in the Fund's investments or in their capacity or willingness to transact may increase the Fund's exposure to this risk. Events that may lead to increased redemptions, such as market disruptions or increases in interest rates, may also negatively impact the liquidity of the Fund's investments when it needs to dispose of them. If the Fund is forced to sell its investments at an unfavorable time and/or under adverse conditions in order to meet redemption requests, such sales could negatively affect the Fund. Securities acquired in a private placement, such as Rule 144A securities, are generally subject to significant liquidity risk because they are subject to strict restrictions on resale and there may be no liquid secondary market or ready purchaser for such securities.  Liquidity issues may also make it difficult to value the Fund's investments.

Management Risk: A strategy used by the Fund's portfolio managers may fail to produce the intended result.

Market/Issuer Risk: The market value of the Fund's investments will move up and down, sometimes rapidly and unpredictably, based upon overall market and economic conditions, as well as a number of reasons that directly relate to the issuers of the Fund's investments, such as management performance, financial condition and demand for the issuers' goods and services. 

Mortgage-Related and Asset-Backed Securities Risk: In addition to the risks associated with investments in fixed-income securities generally (for example, credit, liquidity and valuation risk), mortgage-related and asset-backed securities are subject to the risks of the mortgages and assets underlying the securities as well as prepayment risk, the risk that the securities may be prepaid and result in the reinvestment of the prepaid amounts in securities with lower yields than the prepaid obligations. Conversely, there is a risk that a rise in interest rates will extend the life of a mortgage-related or asset-backed security beyond the expected prepayment time, typically reducing the security's value, which is called extension risk. The Fund also may incur a loss when there is a prepayment of securities that were purchased at a premium. The Fund's investments in other asset-backed securities are subject to risks similar to those associated with mortgage-related securities, as well as additional risks associated with the nature of the assets and the servicing of those assets.

Risk/Return Bar Chart and Table

The bar chart and table shown below provide 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 returns for the one-year, five-year and ten-year periods compare to those 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 information is available online at ngam.natixis.com and/or by calling the Fund toll-free at 800-225-5478.

The chart does not reflect any sales charge that you may be required to pay when you buy or redeem the Fund's shares. A sales charge will reduce your return.

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Fund Summary

Total Returns for Class A Shares

Highest Quarterly Return: Third Quarter 2009, 2.93%
Lowest Quarterly Return: Second Quarter 2013, -1.22%

Average Annual Total Returns
(for the periods ended December 31, 2016)	Past 1 Year		Past 5 Years		Past 10 Years
Class A - Return Before Taxes	-1.54	%	0.52	%	2.76	%
Return After Taxes on Distributions	-2.17	%	-0.26	%	1.77	%
Return After Taxes on Distributions and Sale of Fund Shares	-0.87	%	0.07	%	1.75	%
Class C - Return Before Taxes	-1.14	%	0.20	%	2.22	%
Class T - Return Before Taxes	-1.80	%	0.47	%	2.73	%
Class Y - Return Before Taxes	0.95	%	1.21	%	3.25	%
Bloomberg Barclays U.S. 1-5 Year Government Bond Index	1.02	%	0.80	%	2.76	%

The Fund did not have Class N or Class T shares outstanding during the periods shown above. The returns of Class N and Class T shares would have been substantially similar to the returns of the Fund's other share classes because they would have been invested in the same portfolio of securities and would only differ to the extent the other share classes did not have the same expenses. Performance of Class T shares shown above is that of Class A shares, which have the same expenses as Class T shares, restated to reflect the different sales load applicable to Class T shares.

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 an investor's tax situation and may differ from those shown. After-tax returns shown are not relevant to investors who hold their shares through tax-advantaged arrangements, such as 401(k) plans, qualified plans, education savings accounts, such as 529 plans, or individual retirement accounts. The after-tax returns are shown for only one class of the Fund. The Return After Taxes on Distributions and Sale of Fund Shares for the one-year period exceeds the Return Before Taxes due to an assumed tax benefit from losses on a sale of Fund shares at the end of the measurement period.  After-tax returns for the other classes of the Fund will vary. Index performance reflects no deduction for fees, expenses or taxes.

Management

Investment Adviser

Loomis, Sayles & Company, L.P. 

Portfolio Managers

Christopher T. Harms, Vice President of the Adviser, has served as co-portfolio manager of the Fund since 2012.

Clifton V. Rowe, CFA^®, Vice President of the Adviser, has served as co-portfolio manager of the Fund since 2001.

Kurt L. Wagner, CFA^®, CIC, Vice President of the Adviser, has served as co-portfolio manager of the Fund since 2012.

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Fund Summary

Purchase and Sale of Fund Shares

Class A and C Shares

The following chart shows the investment minimums for various types of accounts:

Type of Account	Minimum Initial Purchase		Minimum Subsequent Purchase
Any account other than those listed below	$	2,500	$	100
For shareholders participating in Natixis Funds' Investment Builder Program	$	1,000	$	50
For Traditional IRA, Roth IRA, Rollover IRA, SEP-IRA and Keogh plans using the Natixis Funds' prototype document (direct accounts, not held through intermediary)	$	1,000	$	100
Coverdell Education Savings Accounts using the Natixis Funds' prototype document (direct accounts, not held through intermediary)	$	500	$	100

Class N Shares

Class N shares of the Fund are subject to a $1,000,000 initial investment minimum. There is no initial investment minimum for certain retirement plans and funds of funds that are distributed by NGAM Distribution, L.P. There is no subsequent investment minimum for these shares.

Class T Shares

Class T shares of the Fund may only be purchased by investors who are investing through an authorized third party, such as a broker-dealer or other financial intermediary, that has entered into a selling agreement with NGAM Distribution, L.P. Investors may not hold Class T shares directly with the Fund. Class T shares are subject to a minimum initial investment of $2,500 and a minimum subsequent investment of $100.  Not all financial intermediaries make Class T shares available to their clients.

Class Y Shares

Class Y shares of the Fund may be purchased by the following entities at the following investment minimums.

A minimum initial investment of $100,000 and the minimum subsequent investment of $100 for:

■

Other mutual funds, endowments, foundations, bank trust departments or trust companies.

There is no initial or subsequent investment minimum for:

■

Wrap Fee Programs of certain broker-dealers, the advisers or NGAM Distribution, L.P. Please consult your financial representative to determine if your wrap fee program is subject to additional or different conditions or fees.

■

Certain Retirement Plans. Please consult your retirement plan administrator to determine if your retirement plan is subject to additional or different conditions or fees.

■

Certain Individual Retirement Accounts if the amounts invested represent rollover distributions from investments by any of the retirement plans invested in the Fund.

■

Clients of a Registered Investment Adviser where the Register Investment Adviser receives an advisory, management or consulting fee.

■

Fund Trustees, former Fund trustees, employees of affiliates of the Natixis Funds and other individuals who are affiliated with any Natixis Fund (this also applies to any spouse, parents, children, siblings, grandparents, grandchildren and in-laws of those mentioned) and Natixis affiliate employee benefit plans.

Due to operational limitations at your financial intermediary, certain wrap fee programs, retirement plans, individual retirement accounts and accounts of registered investment advisers may be subject to the investment minimums described above.

The Fund's shares are available for purchase and are redeemable on any business day through your investment dealer, directly from the Fund by writing to the Fund at Natixis Funds, P.O. Box 219579, Kansas City, MO 64121-9579, by exchange, by wire, by internet at ngam.natixis.com (certain restrictions may apply), through the Automated Clearing House system, or, in the case of redemptions, by telephone at 800-225-5478 or by the Systematic Withdrawal Plan. See section "How Fund Shares are Priced" for details. 

Tax Information

Fund distributions are generally taxable to you as ordinary income or capital gains, except for distributions to retirement plans and other investors that qualify for tax-advantaged treatment under U.S. federal income tax law generally. Investments in such tax-advantaged plans will generally be taxed only upon withdrawal of monies from the tax-advantaged arrangement.

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 the Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other

5

Fund Summary

intermediary and your salesperson to recommend the Fund over another investment. Ask your salesperson or visit your financial intermediary's website for more information.

ULT77-0317

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