The Ultimate Fighter 4 is the fourth season of the mixed martial arts reality television series The Ultimate Fighter. It premiered on August 17, 2006, immediately after the conclusion of UFC Fight Night 6. The finale was aired on November 11, 2006.

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, 2004, 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.