UFC 83: Serra vs St-Pierre 2 was a mixed martial arts event held by the Ultimate Fighting Championship. The event was held on April 19, 2008, at the Bell Centre in Montreal, Quebec, Canada. UFC 83 was the UFC's first event in Canada. It was headlined by UFC Welterweight Champion Matt Serra and UFC Interim Welterweight Champion Georges St-Pierre in a match to unify the championship.

The event on this date was originally scheduled to be called UFC 84, but following the cancellation of a tentatively scheduled March 8, 2008 event in England, the event's title was changed to UFC 83 instead.

Several prominent Canadian fighters were set to compete, including Kalib Starnes, Mark Bocek, Jason MacDonald, Sam Stout, Jason Day and Jonathan Goulet. Patrick Côté was scheduled to fight as well, but was forced to pull out after sustaining an injury in a slip-and-fall accident.

The main event featured a rematch between Matt Serra and Georges St-Pierre from their fight at UFC 69, which Serra had won. The two fighters exchanged harsh words through the media following that fight, which led to the circumstances that surrounded the rematch. St-Pierre cited personal issues for the loss. He said that his father was seriously ill, and that his 17 year old cousin had died in a car accident around the time of the first fight. St-Pierre then claimed that he only accepted the fight with Serra because he thought he could "easily beat this guy." Serra took exception to these comments and responded in a subsequent radio interview by calling St-Pierre a "Frenchy", telling him to "go drink some red wine and go watch a hockey game."

Matthew John Serra (born June 2, 1974) is an American mixed martial artist and Brazilian Jiu-Jitsu black belt. He is a former UFC Welterweight Champion and an ADCC Submission Wrestling World Championship silver medalist. He began practicing martial arts at an early age, first studying kung fu. In the 1990s, he began studying Brazilian Jiu-Jitsu under Renzo Gracie and on May 23, 2000 he obtained his black belt, the first American to do so under Gracie. He is one of only two people in MMA to defeat Georges St-Pierre, the other being UFC Hall of Famer Matt Hughes.

Serra won first place at the Brazilian Jiu-Jitsu Pan American games in 1999 and won third place at the 1999 World Championships in Brazil as a brown belt. Continuing his Martial Arts career, he competed in the ADCC Submission Wrestling World Championship choking out Takanori Gomi, winning a decision over Jean-Jacques Machado, and placing 2nd in the 66–76 kg division. Serra was invited to compete in Pride 9 against Johil de Oliveira but the bout was called off at the last minute when Oliveira was burned in a pyrotechnics accident backstage. Soon after, Matt began to compete in the UFC organization where he built up a record of four wins and four losses. One of the losses was a close decision fight with future Welter and Lightweight champ B.J. Penn which would have earned him a title shot in the failed Lightweight tournament.

Jason Anthony MacDonald (born June 3, 1975) is a Canadian mixed martial artist who is currently fighting with the Ultimate Fighting Championship as a middleweight. He is also a veteran of the Maximum Fighting Championship and TKO Major League MMA in his native country of Canada. He is known for his athleticism and his glass chin. Born and raised in Merigomish, Pictou County, Nova Scotia, MacDonald currently resides in Red Deer, Alberta and fights out of Edmonton, Alberta. MacDonald holds notable victories over Chris Leben, Ed Herman, Joe Doerksen (2x), and Jason Lambert.

MacDonald began his career in local Canadian promotions, including the Maximum Fighting Championship, earning notable wins over UFC veterans Joe Doerksen, Gideon Ray, and Bill Mahood. After racking up a record of 16–7, he made his UFC debut on October 10, 2006, at Ortiz vs. Shamrock 3: The Final Chapter against the favored The Ultimate Fighter 3 finalist Ed Herman. In an upset, MacDonald won the bout via triangle choke in the first round. MacDonald followed up the performance with a win over The Ultimate Fighter 1 veteran Chris Leben via modified guillotine choke in the second round. Both victories earned Submission of the Night honors.

Nathan Parker Quarry (born March 19, 1972) is a retired American mixed martial arts fighter who is most notable for his appearance in The Ultimate Fighter, a reality show from the Ultimate Fighting Championship, as well as co-hosting the show MMA Uncensored Live.

Nate Quarry grew up as a member of the Jehovah's Witnesses, which he later characterized as a cult that controls its members 24 hours a day. Quarry grew up in a sheltered lifestyle and did not even participate in organized sports until age 24, when he first became exposed to mixed martial arts. After a period of self-discovery, Quarry rejected his Jehovah's Witness upbringing, which caused him to become alienated from his family and former friends. He began to associate with others outside of the church and along the way began to train in mixed martial arts fighting. Eventually, Quarry made his way to Team Quest, out of Gresham, Oregon, where he continued to train until mid-2007.

Quarry made his professional mixed martial arts debut in 2001, in a match against Drew McFedries, which he won with a TKO in the second round. After compiling a 5–1 record, Quarry was invited by the UFC to participate in The Ultimate Fighter, a reality television show and mixed martial arts competition featuring up-and-coming MMA talent living and training in seclusion with the UFC. On the show however, Quarry had to drop out of the competition when he suffered an ankle injury during practice, which would have required six weeks to heal. He was asked to stay on as an assistant coach. When he was no longer officially allowed to compete, he allowed Team Quest teammate, Chris Leben (who was already eliminated by Josh Koscheck) to take his place. During his time on the show, he was seen as the role model for Team Couture and would also stand up for Team Liddell member Sam Hoger when others would make fun of him, but confronted him when he was accused of stealing UFC merchandise from the gym.

Rich Jay Franklin II (born October 5, 1974) is an American mixed martial artist and former UFC Middleweight Champion.

Franklin was born to Richard Sr. and Vaila Franklin. The couple divorced when Rich was five years old. He has one biological brother, Greg, and five step-siblings.

Prior to becoming a full time MMA fighter, Franklin graduated from William Henry Harrison High School. He earned a bachelor's degree in mathematics and later earned a master's degree in education at the University of Cincinnati, and taught mathematics at the Oak Hills High School in Cincinnati, Ohio.

Franklin and American Fighter President Jeff Adler created The Keep It In The Ring Foundation to advocate non-violence and build character in youth. This is done through after school sports, martial arts and life skills programs. His nickname "Ace" comes from his resemblance to Jim Carrey, who played the character Ace Ventura. Joe Rogan once called him "An angry Jim Carrey". Franklin made his acting debut in a film called Cyborg Soldier where he plays an escaped super soldier and partners with Tiffani Thiessen.