Sim Cain (born Simeon Cain McDonald, July 31, 1963) is an American drummer, best known as a member of the hard rock group Rollins Band from 1987 to 2000. Critic Michael Azerrad describes Cain's drumming as "a brutal but brainy style that was positively electrifying."
One of his earliest bands was the instrumental group Regressive Aid, and Cain came to greater prominence with Greg Ginn's Gone, another instrumental group. In 1988, Cain briefly played in an early version of Ween's expanded live band alongside fellow Rollins Band member Andrew Weiss, who went under the name The Ween.
His greatest mainstream recognition came with the Rollins Band, however, as the group scored several hit songs on MTV ("Low Self Opinion" and "Liar") during the 1990s.
Cain has also recorded with David Poe, Marc Ribot, and David Shea, and is a regular member of Elliott Sharp's blues-oriented Terraplane group. He also appeared on Ween's 2003 album, Quebec. In the early and mid-2000s, he has appeared regularly in concert with blues guitar great Hubert Sumlin. He was the drummer for the J. Geils Band in 1999 for a reunion tour.
As of 2008, Sim plays regularly with the Billy Hector Band, a blues outfit from the New Jersey shore.