James "The Colossus" Thompson (born December 16, 1978) is a British mixed martial arts (MMA) fighter. He fights as a heavyweight and has appeared in such promotions as Elite Xtreme Combat (EliteXC), Pride Fighting Championship, and Cage Rage. He is known for rushing his opponents at the start of bouts. Thompson grew up in Rochdale, Greater Manchester and later moved to Bristol in 2001. He worked as a bouncer as well as a "debt collector" and "gypsy remover". He also pursued a career in bodybuilding, during which time he used steroids. Thompson took up the sport of wrestling and competed in a several matches before seeing an MMA match featuring Don Frye, which ultimately inspired him to join MMA.

Thompson began his mixed martial arts career fighting in the British promotion Ultimate Combat (UC). He developed a rivalry with Mark "The Shark" Goddard after their bout in Ultimate Combat 6: Battle in the Cage. Thompson won the bout by referee stoppage, but Goddard disputed the result, saying that Thompson had tapped earlier to one of his armbar attempts. A rematch at Ultimate Combat 8: Retribution resulted in an 18 second knockout victory for Thompson. After five straight victories, he faced his first loss to Tengiz Tedoradze at Ultimate Combat X. Tedoradze managed to stop Thompson's initial charge and won by doctor stoppage after the second round. Thompson bounced back with a UC championship bout against Ultimate Fighting Championship (UFC) veteran Dan Severn at Ultimate Combat 11: Eyes of the Beast. Thompson won the five-round bout by unanimous decision.

After defeating Severn, Thompson made his Pride Fighting Championship debut at PRIDE 28 to face Aleksander Emelianenko at Pride 28: High Octane. Despite losing the fight in only eleven seconds, he remained with the organization, earning quick victories over Henry Miller and Giant Silva. Thompson became known to Pride fans for his penchant for rushing at opponents at the opening bell, which became known as 'Gong and Dash'. During this time, Thompson alternated appearances in Japan with fights in British organizations such as Cage Rage.

Thompson's career took a downturn with three consecutive losses to Kazuyuki Fujita, Rob Broughton, and Jon Olav Einemo. However, he followed up with an upset victory over Olympic judo gold medalist Hidehiko Yoshida at PRIDE Shockwave 2006. He next suffered a quick KO at the hands of super heavyweight boxer Eric 'Butterbean' Esch at Cage Rage 20. In his final appearance in Pride, Thompson dominated aging UFC veteran Don Frye to a first round stoppage at Pride 34. Thompson followed up with his final appearance in Cage Rage, losing to Neil Grove by knockout in just 10 seconds.

Thompson cited a lack of quality heavyweight training partners for his poor performances, and switched training camps to join Randy Couture's Xtreme Couture.

Thompson made his EliteXC debut against undefeated 8 - 0 fighter Brett Rogers at the EliteXC: Street Certified on February 16, 2008. Rogers knocked Thompson out in the first round. Despite this loss, Thompson followed up with a headlining appearance at EliteXC: Primetime against streetfighting internet sensation Kevin Ferguson "Kimbo Slice". Entering the fight with a considerably swollen cauliflower ear, Thompson managed to control the first two rounds with effective ground and pound. However, both fighters came into the third round substantially winded. Kimbo landed several unanswered blows to Thompson's face whilst on his feet, one of which burst his cauliflower ear, prompting the referee to stop the fight and declare a TKO in Slice's favour. The stoppage caused some controversy.

On February 6, 2009, Thompson fought Steve Bosse at Strike Box/Titans Fighting's inaugural event in Quebec, Canada. The event was originally scheduled to be conducted under Strike Box's own rules where only boxing, takedowns and standing submissions were allowed, but the rules were not accepted by the province's athletic commission in time for the event. It was therefore instead conducted under MMA rules. Before the event some fighters agreed to fight under Strike Box's proposed rules as a gentleman's agreement, though the referee in charge would not have any choice but to allow ground fighting were it to happen.

Thompson, who later claimed to be unaware of the agreement, proceed to take down, mount and ground and pound Bosse - as allowed under MMA rules - after Bosse went for a standing guillotine choke at the start of the fight. This caused the attending audience to boo Thompson and the referee, unaware of that the fight was technically conducted under MMA rules. Beer cans and eventually chairs were then thrown into the ring, prompting referee Yves Lavigne to stop the match declaring it a no contest.