Robert Clohessy (born June 10, 1958) is an American actor, known for playing Correctional Officer Sean Murphy on the HBO drama Oz. He was also a cast member in the final season of Hill Street Blues.

He has had recurring roles in the ABC daytime drama All My Children, Guiding Light, and appeared in the short lived Fox show New Amsterdam. He also played a semi-minor role in the film "Across the Universe", playing the part of Jude's long-lost father. He was also a series regular in short-lived shows such as Laurie Hill who at that time starred a then-unknown Ellen Degeneres.

He played the role of "Mike" in the Broadway Roundabout Theatre Company revival of Pal Joey, from November 2008 through February 2009. He is currently seen on HBO's new show Boardwalk Empire.