Mark D Fairchild

Thomas Mark Harmon (born September 2, 1951) is an American actor, writer, producer, television director and former football player. He is best known for playing the lead role of Leroy Jethro Gibbs on NCIS. He has appeared in a wide variety of television roles since the early 1970s, including as Dr. Robert Caldwell on St. Elsewhere, Detective Dicky Cobb on Reasonable Doubts, and Dr. Jack McNeil on Chicago Hope.