Thomas Mark Harmon (born September 2, 1951) is an American actor, producer, director and former football quarterback. He is best known for playing the lead role of Leroy Jethro Gibbs in Ncis. He also has appeared in a wide variety of roles since the early 1970s. Initially a college football player, his role on St. Elsewhere led to his being named "Sexiest Man Alive" by People in 1986. After spending the majority of the 1990s as a character actor, he played Secret Service special agent Simon Dono