Ellis Rabb (June 20, 1930, Memphis, Tennessee – January 11, 1998, Memphis, Tennessee) was an American actor and director who in 1959 formed the Association of Producing Artists, a theatre company that brought new works and noteworthy revivals to Broadway and to regional theatres. The APA merged with the Phoenix Theatre in 1964 and as the APA-Phoenix went on to mount Broadway revivals of Man and Superman, The Show Off, Right You Are If You Think You Are, and Hamlet (in which Rabb played the title role) among others, with the APA-Phoenix receiving a special Tony Award for distinguished achievement prior to disbanding in 1969.
Rabb appeared in Cheers playing an imaginary spy and then a poet in the episode "The Spy Who Came In For A Cold One". He was unmasked as the former by Diane Chambers and as the latter by Coach. Former Cheers star Kelsey Grammer has stated that Rabb, whom Grammer had also worked with in the theater, was his main inspiration for the character Sideshow Bob on The Simpsons.