The Ultimate Fighter is an American reality television series and mixed martial arts (MMA) competition produced by the Ultimate Fighting Championship (UFC) and Pilgrim Media Group currently airing on ESPN+. It previously aired for fourteen seasons on Spike TV. The show features professional MMA fighters living together in Las Vegas, Nevada, and follows them as they train and compete against each other for a prized six-figure contract with the UFC. The series debuted on January 17, 2005, with its first episode, "The Quest Begins". To date, there have been thirty one seasons of the show, two per calendar year, some years having only one season. Each season features either one or two weight classes in the tournament.

The historic Forrest Griffin vs. Stephan Bonnar fight in the first season drew millions of viewers to the show and launched the sport into the mainstream. Because of this success, The Ultimate Fighter was regarded as instrumental to the survival and expansion of the UFC and mixed martial arts into the mainstream. Many current and past UFC fighters are alumni of the show, with some competitors going on to become coaches in future seasons. The show has undergone multiple format changes since its inception, including the introduction of the wildcard bout. Many winners have gone on to compete for UFC championships with some becoming UFC champions.