Jeffrey Sinclair is a fictional character on the space opera television series titled Babylon 5. He is the original Commander of the Babylon 5 space station.

Robert Michael O'Hare Jr. was an American actor who performed on stage and television. He was best known for playing the lead role of space station Commander Jeffrey Sinclair in the science fiction television series Babylon 5, a role he left after the first season due to serious mental health issues.