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.

Thomas William Selleck is an American actor. His breakout role was playing private investigator Thomas Magnum in the television series Magnum, P.I. (1980–1988), for which he received five Emmy Award nominations for Outstanding Lead Actor in a Drama Series, winning in 1985. Since 2010, Selleck has co-starred as New York City Police Commissioner Frank Reagan in the series Blue Bloods. From 2005–2015, he portrayed troubled small-town police chief Jesse Stone in nine television films based on the Robert B. Parker novels.