The MAC Commonwealth is an intercollegiate athletic conference affiliated with the NCAA's Division III. It is one of the three conferences that operate under the umbrella of the Middle Atlantic Conferences; the others being the MAC Freedom Conference and the Middle Atlantic Conference, a grouping used for some sports that consists of MAC Commonwealth and MAC Freedom schools. Member institutions are located in Pennsylvania and Maryland.
The league currently has nine full members. Arcadia and Lycoming, which will move from the MAC Commonwealth to the MAC Freedom in 2020, are highlighted in red.
|Albright College||Reading, Pennsylvania||Lions||1856||Private/Methodist||2,304||1999|
|Alvernia University||Reading, Pennsylvania||Golden Wolves||1958||Private/Catholic||2,872||2009|
|Arcadia University||Glenside, Pennsylvania||Knights||1853||Private/Presbyterian||2,473||2008|
|Hood College||Frederick, Maryland||Blazers||1893||Private/Reformed||1,174||2012|
|Lebanon Valley College||Annville, Pennsylvania||Dutchmen||1866||Private/Methodist||1,712||1999|
|Lycoming College||Williamsport, Pennsylvania||Warriors||1812||Private/Methodist||1,272||2007|
|Messiah College||Grantham, Pennsylvania||Falcons||1909||Private/Christian||3,305||1999|
|Stevenson University||Stevenson, Maryland||Mustangs||1947||Private/Catholic||3,621||2012|
|Widener University||Chester, Pennsylvania||Pride||1821||Private/Nonsectarian||6,402||1999|
Enrollment source: 
The MAC will undergo several changes in 2020. The first, announced in April 2019, was the arrival of York College of Pennsylvania in the MAC Commonwealth from the Capital Athletic Conference. The following month, the MAC announced that once York joins, the MAC Commonwealth and MAC Freedom will be realigned so that each will have 9 members. Eastern will move from the MAC Freedom to the MAC Commonwealth, while Arcadia and Lycoming will move in the opposite direction.
|Eastern University||St. Davids, Pennsylvania||Eagles||1952||Private/Baptist||3,420||2020||MAC Freedom|
|York College of Pennsylvania||York, Pennsylvania||Spartans||1787||Private/Nonsectarian||5,564||2020||CAC|
|Elizabethtown College||Elizabethtown, Pennsylvania||Blue Jays||1899||Private/Church of the Brethren||2,416||1999||2014||Landmark|
|Juniata College||Huntingdon, Pennsylvania||Eagles||1876||Private/Church of the Brethren||1,449||1999||2007||Landmark|
|Moravian College||Bethlehem, Pennsylvania||Greyhounds||1742||Private/Moravian||1,792||1999||2007||Landmark|
|Susquehanna University||Selinsgrove, Pennsylvania||Crusaders||1858||Private/Lutheran||1,900||1999||2007||Landmark|
The MAC Commonwealth sponsors intercollegiate athletic competition in men's baseball, men's and women's basketball, women's field hockey, men's golf, men's and women’s soccer, women's softball, men's and women's tennis, and women's volleyball. In addition, members also compete in the Middle Atlantic Conference in men's and women's cross country, men's football, men's and women's ice hockey, men's and women's lacrosse, men's and women's swimming, men's and women's indoor and outdoor track and field, men's volleyball, and men's wrestling
- "MAC Announces Realignment for 2020-21" (Press release). Middle Atlantic Conferences. May 7, 2019. Retrieved August 5, 2019.
- "Best Colleges". U.S. News & World Report.
- "MAC to Add York (Pa.) as 18th Member Beginning in 2020-21" (Press release). Middle Atlantic Conferences. April 2, 2019. Retrieved April 22, 2019.