Magnum, P.I. is an American crime drama television series starring Tom Selleck as Thomas Magnum, a private investigator (P.I.) living on Oahu, Hawaii. The series ran from December 11, 1980, to May 1, 1988, during its first-run broadcast on the American television network CBS. Magnum, P.I. consistently ranked in the top 20 U.S. television programs in the Nielsen ratings during the first five years of its original run, finishing as high as number three for the 1982–83 season. The series entered syndication in 1986 under the title Magnum in order to differentiate reruns from new episodes still airing under the original title on CBS.

A remake series of the same name was ordered to series on May 11, 2018, and premiered on September 24, 2018 on CBS.