Punk rock band from Poway, California formed in 1995. Released three albums between 1998 and 2003; reunited in 2023 and put out a fourth album.

Singer/guitarist Chris Armes and bassist/backing vocalist Jered Herndon attended Poway High School together and played in the band Openfast. When that band broke up, they added classmate Eric Davis on drums and started Area 51. After recording a demo tape, Herndon left and was replaced by Greg Schneider, Davis switched to guitar, Rob Hunter joined on drums, and the band changed its name to Agent 51. They released their first album, Red Alert (1998) on local label Alphabet Records. Wearing matching black suits onstage, they created a loose concept that they were rogue secret agents on the run from the government due to their knowledge of secrets related to extraterrestrial life.

Hunter left the band and was replaced by Mike Levinson. Agent 51's second album, Just Keep Runnin', was released in 2000 on the band's own Suburban Hooligans Records. Its liner notes expanded on their secret agent concept by describing the band members as a rogue agents enhanced with super powers through extraterrestrial DNA and technology, fighting against a secret government organization called "The Agency". Schneider left and was replaced by Sean Scura (formerly of The Classified and Pensive), and Adeline Records re-released the album in 2001.

For their third album, The Red & the Black (2003), on Surfdog Records, the band shifted in a hard rock direction and dropped the secret agent concept. Agent 51 broke up after this album. Davis and Levinson formed 51 Guns with drummer Adam Rapps (ex-Pivit), which later evolved into Arm The Angels. Levinson left this band and reunited with former Agent 51 bassist Greg Schneider in The Megas. Armes later formed The Rattlesnake Aces.

Starting in 2005 Agent 51 played occasional one-off reunion shows every few years. In 2012 the Just Keep Runnin'-era lineup of Armes, Davis, Schneider, and Levinson released two new songs as the Operation Panther E​.​P. The band became active again in 2023, releasing new material including the 2025 album Age of Validation.