NCIS: Los Angeles is an American action crime drama television series combining elements of the military drama and police procedural genres, which premiered on CBS on September 22, 2009. The series follows the exploits of the Los Angeles–based Office of Special Projects (OSP), an elite division of the Naval Criminal Investigative Service that specializes in undercover assignments. NCIS: Los Angeles is the first spin-off of the successful series NCIS and the second series in the NCIS franchise. The series concluded on May 21, 2023, making it the second series in the NCIS franchise to end..

The United States Naval Criminal Investigative Service (NCIS) is the primary investigative law enforcement agency of the U.S. Department of the Navy. Its primary function is to investigate major criminal activities involving the Navy and Marine Corps, though its broad mandate includes national security, counterintelligence, counterterrorism, cyberwarfare, and the protection of U.S. naval assets worldwide. NCIS is the successor organization to the former Naval Investigative Service (NIS), which was established by the Office of Naval Intelligence after the Second World War.