Talented Swede Alexander "The Mauler" Gustafsson landed on the international MMA scene when he entered the Ultimate Fighting Championship at UFC 105: Couture vs. Vera in November of 2009. Gustafsson was a virtual unknown at that time despite an 8-0 record with seven stoppages (six of them by strikes). Over the coming year, Gustafsson proved he belonged among the MMA elite by compiling a 2-1 record with the world's biggest cagefighting promotion. Gustafsson fights out of Stockholm, Sweden. He trains with Allstars Training Center and Alliance MMA.

Gustafsson's first loss came to the vaunted newcomer and highly touted prospect, American freestyle wrestler Phil Davis. Following the loss, Gustafsson immediately began training with Davis for his very next bout alongside Brandon Vera, Joey Beltran and others at Team Alliance. The lesson in humility paid off in the form of the second of Gustafsson's two wins, which came against European striking legend Cyrille "The Snake" Diabate. Despite taking place on UFC 121's untelevised preliminary undercard, the first round submission victory was Gustafsson's highest profile win to date and a coming out party for the young fighter.

Gustafsson followed up that win with a first round submission of James Te Huna. Next in line for Gustaffon was two impressive TKO victories over tough veterans Matt Hamill and Vladimir Matyushenko, moving him even further up the ranks. In April 2012 he won a unanimous decision over Thiago Silva. In his next fight at UFC on FOX 5 he decisively defeated Mauricio "Shogun" Rua in a fight that catapulted him right to the top of the division. During the post-fight press conference The Mauler expressed his desire to fight as soon as possible instead of waiting until summer 2013 for his upcoming UFC Light Heavyweight Title shot. Gustafsson would get his wish as the UFC set him up to welcome Gegard Mousasi to the UFC as the main event for UFC on Fuel TV 9. However less than a week before the fight it was announced that The Mauler had received a cut during training and was not cleared to fight so they had to cancel the match.

Gustafsson got his light heavyweight title shot against division champion Jon "Bones" Jones at UFC 165 in Toronto. The fight was afterwards described as a five round war in which the swede gave the champion his toughest challenge to date. Gustafsson lost the bout by judges call, a unanimous decision in favor of the champion. UFC fans and media alike thought, since the fight was so close fought that a rematch should be schedueled immediately. This did not materialize however, and Gustafsson instead got Antonio Rogerio Noguiera as his next opponent.

Only days after it was announced, Nogueira had to pull out due to an injury. News would surface later that Noguiera never officially accepted the fight, and the fight announcement should never have gone public. Gustafsson got a new opponent in Jimi Manuwa, and they were schedueled to fight on March 8th 2014 in London, England. Gustaffson would finish Manuwa by TKO with an uppercut in the 2nd round handing the up and comer his first loss. The win also earned Gus the Fight of the Night bonus as well as the Performance of the Night bonus. Following the win Gus would look to earn himself a rematch against the champion when he faced Anthony Johnson. However Rumble had different plans and would finish Gus in the first round by TKO.