MAGNUM, P.I. Theme HD MAGNUM, P.I. Theme Magnum, P.I. is an American television series starring Tom Selleck as Thomas Magnum, a private investigator living on Oahu, Hawaii. The series ran from 1980 to 1988 in first-run broadcast on the American CBS television network. According to the Nielsen ratings, Magnum, P.I. consistently ranked in the top […]