Spencer William Fisher (born May 9, 1976) is an American mixed martial arts fighter from Brevard, North Carolina. He trains with the Miletich Fighting Systems camp and currently fights in the lightweight division of the Ultimate Fighting Championship promotion.

He made his UFC debut at Ultimate Fight Night 2, scoring a second-round submission victory over Thiago Alves. He then defeated Aaron Riley at Ultimate Fight Night 3 by TKO after the first round. Perhaps Fisher's most notable early fight was with Canadian kickboxer Sam Stout on the undercard of UFC 58. When Stout's original opponent Kenny Florian sustained an injury in training that left him unable to compete, Fisher took the fight on very late notice, reportedly having to cut twenty pounds in the final two days leading up to the match. Although Fisher seemed to land harder punches, Stout landed more, and came away with a split decision.

Fisher returned at UFC 60 against Matt Wiman and won by knockout in the second round, hitting Wiman with a flying knee that forced referee John McCarthy to stop the bout. Fisher was able to record another first round TKO at UFC 64 against Dan Lauzon. His win streak came to a halt at Ultimate Fight Night 8, where he was defeated in round two by TKO (strikes) by Hermes Franca.

In a rematch of their UFC 58 match, Fisher defeated Sam Stout at Fight Night 10 by unanimous decision after three rounds. Fisher was scheduled to fight Din Thomas at UFC Fight Night 11, but was forced to withdraw due to a staph infection. Ironically, Fisher's replacement for this match was Kenny Florian, who Fisher had replaced in the UFC 58 fight against Sam Stout.

Fisher fought Frankie Edgar at UFC 78: Validation on November 17, 2007. Fisher lost this fight by unanimous decision. Fisher's next fight was scheduled to be against Marcus Aurelio at UFC Fight Night 13, but he was forced to withdraw due to a shoulder injury. With his shoulder healed, Fisher was next scheduled to fight Jeremy Stephens at The Ultimate Fighter: Team Rampage vs. Team Forrest Finale on June 21, 2008. Fisher won by unanimous decision.

Fisher defeated Shannon Gugerty at UFC 90 in Chicago on October 25, 2008.