The fourth season of the American crime and action drama Magnum P.I. premiered on October 1, 2021, on CBS, for the 2021–22 television season. It concluded on May 6, 2022. The series is a remake of the 1980 series of the same name and centers on Thomas Magnum, a former Navy SEAL who works as a private investigator and solves mysteries with his business partner Juliet Higgins and other friends. It stars Jay Hernandez, Perdita Weeks, Zachary Knighton, Stephen Hill, Amy Hill, and Tim Kang. The season was ordered on April 15, 2021, and consisted of twenty episodes. On May 12, 2022, it was announced that CBS had canceled the series after four seasons, however, on June 30, 2022, the series was picked up by NBC for a fifth and sixth seasons, consisting of twenty episodes. Dennis Chun appeared in the sixteenth episode of the season as his Hawaii Five-0 character in a minor crossover event. The season premiere, "Island Vibes", was watched by 5.23 million viewers.

Niall Matter is a Canadian-American actor.