The fifteenth season of the American police procedural drama NCIS premiered on September 26, 2017, in the same time slot as in the previous seasons, Tuesdays at 8 PM. The season premiere was watched by 17.42 million viewers, picking up two months after Gibbs and McGee were last seen fighting a group of rebels in Paraguay and focused on the aftermath of those events. The season concluded on May 22, 2018 and contained 24 episodes.

NCIS is an American military police procedural television series and the first installment within the NCIS media franchise. The series revolves around a fictional team of special agents from the Naval Criminal Investigative Service (NCIS), combining elements of the military drama and police procedural genres with comedy. The concept and characters were initially introduced with two episodes of the CBS series JAG ; as a spin-off from JAG, the series premiered on September 23, 2003, on CBS. To date, it has entered into the 21st full season and has gone into broadcast syndication on the USA Network. Donald P. Bellisario and Don McGill are co-creators and executive producers of the premiere member of the NCIS franchise. As of 2022, NCIS is the third-longest-running scripted, live-action U.S. prime-time TV series currently airing, surpassed only by Law & Order: Special Victims Unit (1999–present) and Law & Order ; it is the seventh-longest-running scripted U.S. prime-time TV series overall.