CSI: Crime Scene Investigation is an American crime drama television series that trails the investigations of a team of Las Vegas forensic scientists as they unveil the circumstances behind mysterious and unusual deaths and other crimes. The show was created by Anthony E. Zuiker and is filmed primarily at Universal Studios in Universal City, California. The pilot episode was first broadcast on October 6, 2000, and eight seasons have been aired. CSI currently airs on Thursdays, at 9PM on CBS. In Canada, the show airs on CTV at 8PM.

CSI is produced by Jerry Bruckheimer Television and CBS Productions, which became CBS Paramount Television in the fall of 2006. Formerly a co-production with the now-defunct Alliance Atlantis Communications, that company's interest in the series is now owned by investment firm GS Capital Partners, an affiliate of Goldman Sachs. CBS Paramount acquired AAC's international distribution rights to the program.

The show has been heavily criticized—almost since its debut—by police and district attorneys, who felt CSI portrayed an inaccurate image of how police solve crimes, and by the Parents Television Council, who noted the level and gratuitousness of graphic violence, images and sexual content seen on the show. Nevertheless, CSI became the most-watched show on American television by 2002. The success of the show encouraged CBS into producing a franchise, starting in May 2002 with the spin-off CSI: Miami and then again in 2004 with CSI: NY .

The show is now in syndication and reruns are currently broadcast on Spike.

CBS renewed the show for a ninth season, which began airing on October 9, 2008. With the departures of William Petersen and Gary Dourdan, the ninth season will include new characters played by Lauren Lee Smith and Laurence Fishburne. The character of Lady Heather will return in episode 905 and The Miniature Killer will return in episode 907. Some of the California locations include the Verdugo Hills High School, UCLA's Royce Hall, the Pasadena City Hall and, as of October 2007, the California State University, shooting has moved away from Santa Clarita, the city and the surroundings have proven so versatile that CSI still shoots some of its outdoor scenes there.