Bobby Southworth (born December 16, 1969) is an American mixed martial arts fighter. He fights as a light heavyweight. He has also fought in PRIDE FC and appeared on Season 1 of The Ultimate Fighter. He is the former Strikeforce Light Heavyweight Champion.

Southworth's first major exposure in the mixed martial arts world was when he faced Vitor Belfort at PRIDE 13. Southworth was overwhelmed by the Brazilian veteran and lost by rear naked choke in the first round.

Bobby then appeared on Season 1 of The Ultimate Fighter. He won his first preliminary fight against Lodune Sincaid, but lost the second versus Stephan Bonnar by split decision. Bobby returned to the house as a possible replacement for Forrest Griffin, should he not have been medically cleared to fight in the semifinals, but Forrest's cut healed safely and Southworth did not fight again until the undercard of the finale, where he was defeated by Sam Hoger. It was a unanimous decision victory for Sam Hoger.

Southworth then moved to Strikeforce, where his first fight was against James "The Sandman" Irvin. The bout was declared a No-Contest after a mere 17 seconds when in a freak accident Southworth and Irvin's clinch pressed against the cage, pushing open the cage door and causing Irvin to fall out of the ring. In his next fight, Southworth was given the opportunity to fight for Strikeforce's vacant light heavyweight championship against Vernon "Tiger" White. Southworth won a decision victory, taking White down repeatedly and controlling the pace of the match. Southworth's next fight was a non-title bout against Anthony Ruiz, a fight that Ruiz won by way of TKO(cut) in round 2. A rematch was set up, but this time it would be for Southworth's championship. In a rather slow-paced yet effective fight, Southworth defeated Ruiz via 5-round Unanimous Decision on June 27, 2008.

In his next title defense, at Strikeforce: Destruction on November 21, 2008, Southworth lost the light heavyweight championship against, former UFC Light Heavyweight Champion, Renato Sobral "Babalu" by TKO(cut) of the 1st round at 5:00. Southworth was winning the opening frame, having scored a takedown and controlling the clinch, until "Babalu" opened up a horrendous gash above Bobby's left eye with ten seconds to go. "Big" John McCarthy stopped the action to let doctors inspect, and Southworth finished the round by dropping "Babalu" with a punch just before the bell. However, when doctor got a better look at the wound between rounds, Southworth was declared the loser due to the size and depth of the cut. Southworth has said he would like a rematch, and Sobral has verbally agreed.

As a longtime member of Team AKA (American Kickboxing Academy), in San Jose, CA; Bobby has recently started teaching at a new AKA gym in Sunnyvale, CA. Bobby Southworth is a Black Belt in Brazilian Jiu-Jitsu and teaches the Jiu-Jitsu class at AKA Sunnyvale.