What year did CSI end its original run?

CSI: Crime Scene Investigation ended its original run in 2015. The main series concluded with the two-hour finale "Immortality," which aired on CBS on September 27, 2015, after 15 seasons and 337 episodes.

The show's final regular season was season 15, which began in September 2014. Its eighteenth and final standard episode was "The End Game," broadcast on February 15, 2015. Because the feature-length finale aired later in the year, some episode lists distinguish between the end of the regular season and the end of the entire series.

That distinction explains why 2015 is the canonical answer. The season itself finished earlier, but CSI as a television series remained unfinished until "Immortality" was broadcast in September. The finale brought back original stars William Petersen and Marg Helgenberger alongside the later cast.

CSI's conclusion did not end the wider franchise. CBS later launched CSI: Vegas, a sequel series that returned to the Las Vegas setting and premiered in 2021. That revival is separate from the original run, which ended in 2015.