Leroy Jethro Gibbs is the special agent in charge on NCIS.

Gibbs joined the United States Marine Corps instead of attending college. He became a Scout Sniper.

In his free time, he is occasionally shown in his basement building a boat, which he named after his daughter.

Gibbs' age has never been revealed, but it was shown that he was born in rural Stillwater, Pennsylvania. His father, Jackson Gibbs, owns a store (the Stillwater General Store) in the same town.

It has been mentioned in the episode "Frame Up" that Gibbs' father was possibly in the United States Army Air Force because Gibbs refers to a pin-up on his father's P-51 Mustang.

He is named after his father's friend, Leroy Jethro, who was his business partner in the store after having worked together in the coal mines. The younger Gibbs left Stillwater in 1976 at the approximate age of 18-20 and, according to his own statements, did not return for over 30 years.

At NCIS, Gibbs is portrayed as a consummate organizer, disciplined and demanding. These traits often put him in a stand-off with other authorities when pressure is being asserted at his team.

He remains a Marine reservist.

Before the time in which NCIS is set, Gibbs travelled extensively on operations, particularly in Eastern Europe, demonstrated by many flashbacks, many including Director Jenny Shepard.

Gibbs displays a continuous urgency about the investigation he pursues, specifically when being given technical information about, complex subject matter.

The typical response to such information is "Give it to me in English", thus forcing the expert to get to the point, as well as making it easy on the audience.

Gibbs has been married three times and had one daughter named Kelly.