Magnum, P.I. is an American crime drama television series starring Tom Selleck as Thomas Magnum, a private investigator living on Oahu, Hawaii. The series ran from 1980 to 1988 during its first-run broadcast on the American television network CBS. According to the Nielsen ratings, Magnum, P.I. consistently ranked in the top twenty U.S. television programs during the first five years of its original run in the United States.