Peter Wentz (born June 5, 1979) was the bassist and primary lyricist for Fall Out Boy. He grew up near Wilmette, IL. He owns his own clothing company, Clandestine Industries, which distributes hoodies, beanies, and Wentz's book, The Boy With The Thorn In His Side, after The Smiths song of the same name.

The book is about nightmares he had as a child. Wentz also heads his own record label; Decaydance records. Wentz has also establish a film company, known as Bartskull films. Wentz was in a hardcore band during his high school career, called Racetraitor, with current bandmate Joe Trohman.

Wentz was featured on vocals and Trohman on bass. He was married to Ashlee Simpson from 2008 to 2011. The couple's son, Bronx Mowgli Wentz, was born on November 20, 2008.