Mark Harmon has left “NCIS” as a regular cast member after 18 seasons (plus 4 episodes) playing the show’s main character, Leroy Jethro Gibbs. “As an executive producer and dear friend, Mark continues to be an integral part of the fabric of the show. Our north star has always been staying true to our characters, and that truth has always guided the stories we tell and where those characters go. So regarding the future of Gibbs, as long-time fans of the show may have noticed over the years…never count Leroy Jethro Gibbs out,” Showrunner Steven Binder said in a statement. CBS declined to comment on whether or not Harmon will reprise the role in future episodes.