Peter Lewis Kingston Wentz III (born June 5, 1979) is an American musician and singer-songwriter, most famous for his work with the Chicago-based band Fall Out Boy. In recent years, he has also become an entrepreneur.

Wentz was primarily involved in the Chicago hardcore punk scene and was in several bands in the late 1990s. These included First Born, Extinction, Arma Angelus (alongside Tim McIlarth, frontman of Rise Against), Yellow Road Priest, and Racetraitor. He and Arma Angelus' bassist Joe Trohman founded the pop-punk band Fall Out Boy after Trohman introduced Pete to a musical acquaintance, Patirick Stump. Andy Hurley agreed to drum part-time, but only joined the band full-time later. In 2004, Arma Angelus, the band in which Wentz was the vocalist/screamer, played its last show.