Magnum P.I. is an American action drama television series developed by Peter M. Lenkov and Eric Guggenheim. It stars Jay Hernandez as Thomas Magnum, the titular private investigator and former Navy SEAL who solves crimes in Hawaii. It is a reboot of the original series of the same name created by Donald P. Bellisario and Glen A. Larson, which aired from 1980 to 1988. The series co-stars Perdita Weeks, Zachary Knighton, Stephen Hill, Amy Hill, and Tim Kang.

It was ordered to series in May 2018, and premiered on September 24, 2018, on CBS. On October 19, 2018, it was announced that the series had received a full season order from CBS. In April 2021, the series was renewed for a fourth season, which premiered on October 1, 2021. Despite being a Top 25 show in viewers, in May 2022, the series was canceled after four seasons, following the network's failure to reach a new agreement with rights holders CBS Studios and Universal Television. On June 30, 2022, the series was picked up by NBC with a two-season, twenty-episode order, later clarified to be produced and broadcast as a two-part fifth season. The fifth season premiered on February 19, 2023. In June 2023, it was announced that the fifth season would be the final season. The series ended on January 3, 2024.

Magnum P.I. takes place in the same fictional universe as two other series, both also developed by Lenkov and both also reboots of earlier crime shows: Hawaii Five-0 and MacGyver. The three shows have been collectively referred to as the "Lenkov-verse". Initially, the series aired on Monday nights at 9:00 p.m., but aired its latter three CBS seasons on Friday nights in the same timeslot, immediately followed by Blue Bloods starring Tom Selleck, who portrayed the title character from the original series.