Peter K. Sell , (born August 5, 1982 in West Islip, New York) is an American mixed martial artist specializing in Brazilian Jiu Jitsu. He is a black belt under teacher and fellow mixed martial artist Matt Serra in East Meadow, New York, and has trained extensively under striking coach Ray Longo in Garden City, New York. A member of the Serra-Longo Fight Team, Sell fights as a Welterweight in the UFC.

Sell made his debut with the UFC at UFC 51, defeating Phil Baroni by guillotine choke submission in what was considered a major upset.

Sell was then seen as a middleweight contestant on The Ultimate Fighter: The Comeback, which premiered on August 17, 2006. He entered the competition alongside Matt Serra, who competed one weight class below Sell in the welterweight division. Sell defeated "Chainsaw" Charles McCarthy to move on the semi-finals of the competition, where he lost to the ultimate winner of the tournament; Travis Lutter. Although Sell did not proceed the finals, he was featured on the undercard of the season finale where he lost to Scott Smith by knockout.

He then fought and lost to Thales Leites at UFC 69. His next fight was a rematch against Nathan Quarry, at UFC Fight Night 11. Sell lost the fight by KO(Punch).

Pete made his second appearance on The Ultimate Fighter as a trainer for Team Serra for season 6, The Ultimate Fighter: Team Hughes vs. Team Serra.

Pete dropped down to welterweight for his latest match; a victory over Josh Burkman at UFC 90 in Chicago, Ill. by Unanimous Decision (29-28).