Robert Clohessy (born June 10, 1958) is an American actor best known for his role as corrections officer Sean Murphy in the HBO drama Oz. He was also a member of the cast in the final season of the series Hill Street Blues.

He had recurring roles on the ABC daytime drama All My Children, Guiding Light, and also appeared on the short-lived Fox show New Amsterdam. He also played a supporting role in the film Across the Universe, playing Jude's long-lost father. In addition, he was a regular on short-lived series such as Laurie Hill, which at the time starred the then-unknown Ellen DeGeneres.

He played the role of "Mike" in the Broadway revival of the musical Pal Joey by the Roundabout Theatre Company from November 2008 to February 2009. He can currently be seen in the new HBO show Boardwalk Empire.