FPA Flexible Fixed Income Fund

Institutional Class Ticker: FPFIX
Advisor Class Ticker: FFIAX

A series of Investment Managers Series Trust III

Supplement dated September 12, 2024, to the
Prospectus dated April 30, 2024, as supplemented.

Effective immediately, the "Average Annual Total Returns" table on page 10 of the Prospectus is deleted in its entirety and replaced with the following:

¹​  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 upon an investor's tax situation and may differ from those shown. After-tax returns presented here are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts ("IRAs"). Early withdrawal from a 401(k) account or an IRA could lead to taxation of the withdrawn amount as ordinary income and could be subject to an additional tax penalty. The after-tax returns on distributions and sale of Fund shares may be higher than returns before taxes due to the effect of a tax benefit an investor may receive from the realization of capital losses that would have been incurred on the sale of Fund shares. After-tax returns are shown for Institutional Class Shares only and after-tax returns for classes other than Institutional Class will vary from returns shown for Institutional Class.