Rajesh "Raj" Ramayan Koothrappali, Ph.D. is a fictional character on the CBS television series The Big Bang Theory, portrayed by Indian actor Kunal Nayyar. He is one of four main male characters in the show, alongside Howard Wolowitz, Sheldon Cooper, and Leonard Hofstadter, to appear in every episode of The Big Bang Theory. Raj is based on a computer programmer that the show's co-creator, Bill Prady, knew when he was a programmer.

The Big Bang Theory is an American television sitcom created by Chuck Lorre and Bill Prady, both of whom served as executive producers and head writers on the series, along with Steven Molaro. It aired on CBS from September 24, 2007, to May 16, 2019, running for 12 seasons and 279 episodes.