Mark Harmon (born September 2, 1951, in Burbank, California) is an American actor, producer and director. The son of football star Tom Harmon and actress Elyse Knox, he played college football at UCLA before turning to acting in the mid-1970s. He became known for St. Elsewhere and Chicago Hope and starred as Leroy Jethro Gibbs on NCIS from 2003 to 2021, a character introduced on JAG, also serving as a producer of the series. He received an Emmy nomination for his recurring role as Secret Service agent Simon Donovan on The West Wing, and his film work includes Summer School, The Presidio, Wyatt Earp and Freaky Friday.