Thomas Mark Harmon is an American actor. He played 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, he was named "Sexiest Man Alive" by People magazine in 1986, due largely to his role as Dr. Robert Caldwell on St. Elsewhere. After spending the majority of the 1990s as a character actor, he played Secret Service special agent Simon Donovan in a four-episode story arc in The West Wing in 2002, receiving an Emmy Award nomination for the role.Harmon's character of NCIS special agent Leroy Jethro Gibbs was introduced in a guest starring role in two episodes of JAG. From 2003 to 2021, Harmon starred in the spinoff NCIS as the same character.