# EDGAR Filing Document

**Accession Number:** 0000225604
**File Stem:** 0000912938-23-000302
**Filing Date:** 2023-3
**Character Count:** 5425
**Document Hash:** afcabe7fdeef83e9bbcedbb16ba1a551
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0000912938-23-000302.hdr.sgml**: 20230329

**ACCESSION NUMBER**: 0000912938-23-000302

**CONFORMED SUBMISSION TYPE**: 497

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20230329

**DATE AS OF CHANGE**: 20230329

**EFFECTIVENESS DATE**: 20230329

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** MFS SERIES TRUST III
- **CENTRAL INDEX KEY:** 0000225604
- **IRS NUMBER:** 046414785
- **STATE OF INCORPORATION:** MA
- **FISCAL YEAR END:** 0131

**FILING VALUES:**
- **FORM TYPE:** 497
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 002-60491
- **FILM NUMBER:** 23771901

**BUSINESS ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **STREET 2:** 21ST FLOOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199
- **BUSINESS PHONE:** 18006372929

**MAIL ADDRESS:**
- **STREET 1:** 111 HUNTINGTON AVENUE
- **STREET 2:** 21ST FLOOOR
- **CITY:** BOSTON
- **STATE:** MA
- **ZIP:** 02199

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MFS SERIES TRUST III /MA
- **DATE OF NAME CHANGE:** 19940411

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MFS HIGH INCOME FUND
- **DATE OF NAME CHANGE:** 19930408

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** MASSACHUSETTS FINANCIAL HIGH INCOME TRUST
- **DATE OF NAME CHANGE:** 19920703

## Series and Classes Contracts Data

### MFS Municipal High Income Fund (Series ID: S000002429)

---

|  |  |  |
|:---|:---|:---|
| Class Name | Ticker Symbol | Class ID   |
| A          | MMHYX         | C000006488 |
| B          | MMHBX         | C000006489 |
| C          | MMHCX         | C000006490 |
| I          | MMIIX         | C000103072 |
| R6         | MMHKX         | C000191232 |

---

## Series and Classes Contracts Data

### MFS Municipal High Income Fund (Series ID: S000002429)

| Class ID   | Class Name   | Ticker Symbol   |
|:---|:---|:---|
| C000006488 | A            | MMHYX           |
| C000006489 | B            | MMHBX           |
| C000006490 | C            | MMHCX           |
| C000103072 | I            | MMIIX           |
| C000191232 | R6           | MMHKX           |

![](image0.jpg)

SUPPLEMENT TO THE PROSPECTUS

*Supplement dated March 29, 2023, to the Prospectus dated May 31, 2022.*

MFS<sup>®</sup> Municipal High Income Fund

------

#### Effective immediately, the section entitled "Portfolio Manager(s)" under the main heading entitled "Summary of Key Information" is restated in its entirety as follows:

#### Portfolio Manager(s)

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; **Portfolio Manager** | **Since** | **Title** |
| &nbsp;&nbsp; Jason Kosty | 2021 | Investment Officer of MFS |
| &nbsp;&nbsp; Megan Poplowski | March 2022 | Investment Officer of MFS |
| &nbsp;&nbsp; Geoffrey Schechter | 2002 | Investment Officer of MFS |

---

#### Effective immediately, the section entitled "Portfolio Manager(s)" under the main heading entitled "Management of the Fund" is restated in its entirety as follows:

#### Portfolio Manager(s)
Information regarding the portfolio manager(s) of the fund is set forth below. Further information regarding the portfolio manager(s), including other accounts managed, compensation, ownership of fund shares, and possible conflicts of interest, is available in the fund's SAI.

---

| | | |
|:---|:---|:---|
| &nbsp;&nbsp;&nbsp; **Portfolio Manager** | &nbsp;&nbsp;&nbsp; **Primary Role** | &nbsp;&nbsp;&nbsp; **Five Year History** |
| &nbsp;&nbsp; Jason Kosty | &nbsp;&nbsp; Portfolio Manager | &nbsp;&nbsp; Employed in the investment area of MFS since 2003 |
| &nbsp;&nbsp; Megan Poplowski | &nbsp;&nbsp; Portfolio Manager | &nbsp;&nbsp; Employed in the investment area of MFS since 2015 |
| &nbsp;&nbsp; Geoffrey Schechter | &nbsp;&nbsp; Portfolio Manager | &nbsp;&nbsp; Employed in the investment area of MFS since 1993 |

---

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