NCIS is a popular American military police procedural that premiered on CBS on September 23, 2003, as a spin-off from JAG, created by Donald P. Bellisario and Don McGill. After a slow start, it became a cultural phenomenon, being voted "America's favorite television show" in 2011 and becoming the most-watched U.S. series in 2012-13, eventually surpassing Gunsmoke as CBS's longest-running scripted primetime series. The show follows the Major Case Response Team (MCRT) at the Washington Navy Yard, investigating crimes involving the Navy and Marine Corps, originally led by Mark Harmon's Leroy Jethro Gibbs before Alden Parker took over in season 19. The franchise has expanded with spin-offs like NCIS: Los Angeles, NCIS: New Orleans, the prequel NCIS: Origins, and the Paramount+ series NCIS: Tony & Ziva. As of 2025, it ranks as the third-longest-running scripted live-action American prime-time show currently airing, and it has been renewed through season 24, set to premiere on October 6, 2026.