CSI: Crime Scene Investigation, also referred to as CSI and CSI: Las Vegas, is an American procedural forensics crime drama television series that ran on CBS from October 6, 2000, to September 27, 2015, spanning 15 seasons. It is the first series in the CSI franchise. The series originally starred William Petersen, Marg Helgenberger, Gary Dourdan, George Eads, Jorja Fox and Paul Guilfoyle. Other cast members included Eric Szmanda, Robert David Hall, Louise Lombard, Wallace Langham, Lauren Lee Smith, Ted Danson, Laurence Fishburne, and Elisabeth Shue. The series concluded with a feature-length finale, "Immortality".

William Louis Petersen is an American actor. He is best known for his role as Gil Grissom in the CBS drama thriller series CSI: Crime Scene Investigation (2000–2015), for which he won a Screen Actors Guild Award and was nominated for a Golden Globe Award; he was further nominated for three Primetime Emmy Awards as a producer of the show. He reprised his role as Gil Grissom in the sequel CSI: Vegas, which premiered on October 6, 2021.