CSI: Crime Scene Investigation (commonly referred to as CSI or CSI: Las Vegas) is a popular, Emmy Award-winning CBS 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 crimes committed. First aired in October 2000, the show has since spawned two spinoffs, each enjoying their own success. The first spin-off, which debuted in September 2002, is set in Miami (CSI: Miami) and the show's second is set in New York City (CSI: NY) debuted in September 2004. CSI is produced in partnership with the Canadian media company Alliance Atlantis. On May 16, 2007, CBS renewed the show for an eighth season. Season 8 began production in July and began airing on Thursday September 27, 2007.

Stylistically, the show has drawn favorable comparisons to Quincy and The X-Files. The show's gadgets and occasional usage of yet-to-be-invented technology have moved the show nominally into the genre of science fiction and garnered it a 2004 Saturn Award nomination for best network television series. The series also occasionally lapses into the realm of fantasy, such as a 2006 episode, "Toe Tags" which is told from the point of view of several corpses in the CSI lab who reanimate and discuss their deaths with each other.

The series is known for its unusual camera angles, percussive editing techniques, hi-tech gadgets and vehicles (the GMC CSI Mobile Analysis Unit), detailed technical discussion, and graphic portrayal of bullet trajectories, blood spray patterns, organ damage, methods of evidence recovery (e.g. fingerprints from the inside of latex gloves), and crime reconstructions. This technique of shooting extreme close-ups, normally with explanatory commentary from one of the characters is referred to in the media as the "CSI shot". Many episodes feature lengthy scenes in which experiments, tests, or other technical work is portrayed in detail, usually with minimal sounds effects and accompanying music — a technique reminiscent of Mission: Impossible. Often the lighting, composition, and mise-en-scene elements are heavily influenced by avant-garde film.

Even though violence plays an important role in the series, the investigators rarely have to resort to violence or the use of deadly force, contrary to both more violent spin-offs CSI: Miami and CSI: NY. In fact, at least one member of the Las Vegas crime lab has expressed distaste for carrying a firearm (Gil Grissom), and at least two others have mentioned having barely passable firearms expertise (Warrick Brown and Nick Stokes).

Although most episodes cover the solving of two (usually unrelated) cases, a few episodes focus on a single case.