This is a list of Ultimate Fighting Championship (UFC) champions in each weight division.

At the time of the UFC's inception in 1993, the sport of mixed martial arts was unsanctioned in the United States, and it did not include weight classes. Instead of the traditional championship model, tournaments were held with the winner receiving a permanent appellation. In response to criticism from Senator John McCain that saw the loss of its television deal and the banning of the sport in thirty-six states, the UFC increased its cooperation with state athletic commissions and introduced weight classes in 1997.

The original codification for weight classes introduced only two divisions: heavyweight, which grouped competitors above 200 pounds (91 kg), and lightweight, which encompassed all other competitors. The UFC would later rename its lightweight division to middleweight and add lightweight 170 pounds (77 kg) and bantamweight 155 pounds (70 kg) divisions. In 2000, the New Jersey State Athletic Control Board completely took over regulation in its home state, and its rules and weight classes became the de facto rule set for mixed martial arts. The UFC realigned their weight classes to comply with the new regulations in 2001.

Cain Velasquez Ramirez (born July 28, 1982) is a Mexican American mixed martial artist fighting in the Ultimate Fighting Championship where he is a former UFC Heavyweight Champion. He is a two-time All-American collegiate wrestler from Arizona State University in Tempe, Arizona, and a Junior College National Champ at Iowa Central Community College. He is a two-time 5A state champion in Arizona, compiling a record of 110–10 for Kofa High School in Yuma, Arizona. Cain Velasquez is ranked #2 in the heavyweight division.

Velasquez, a Mexican American, was born on July 28, 1982 in Salinas, California to Efrain and Isabel Velasquez. Velasquez's father, Efrain, came from Mexico to the United States illegally. Efrain met his wife Isabel, married her, and gained US citizenship. Velasquez has two siblings, Efrain, Jr., and Adela. He was raised in Yuma, Arizona. He graduated from Kofa High School, where he compiled a record of 110–10 in four years of wrestling, including winning the 5A Arizona Wrestling Championship twice. Velasquez also played football for three years. As a senior, he served as Captain of both his wrestling and football teams.

Frank James Edgar (born October 16, 1981) is an American mixed martial artist, who competes as a lightweight in the Ultimate Fighting Championship and is a former UFC Lightweight Champion. His first career loss came against Gray Maynard in 2008, which marked the beginning of a noted rivalry. He later avenged the loss to Maynard with a KO victory in 2011. As of March 2012, he is ranked as the #2 lightweight in the world by Sherdog.com.

Born and raised in Toms River, New Jersey, Frankie Edgar wrestled at Toms River High School East, making it to the New Jersey state championship tournament on three occasions, placing second as a junior and fifth as a senior. Edgar is the oldest of 3 children, Edgar went on to compete in the NHSCA Senior Nationals and placed second before he finished high school. He continued wrestling at Clarion University of Pennsylvania, where he qualified for the nationals all four years there. Edgar is also an assistant coach for the Rutgers University wrestling team.

Edgar entered his first mixed martial arts fight with only a few weeks of training outside of his wrestling background. Edgar originally trained with Rob Guarino of Rhino Fight Team, but today he is part of the Gracie system under Ricardo Almeida in Hamilton, NJ. Since seventh grade Edgar has wrestled with Steve Rivera at Elite Wrestling NJ in Jackson, NJ. His boxing trainer is Mark Henry of Millstone, NJ.

Anderson da Silva (Portuguese pronunciation: [ˈɐ̃deʁsõ ˈsiwvɐ]; born April 14, 1975) is a Brazilian mixed martial artist. He is the current UFC Middleweight Champion and the promotion's longest reigning champion. With 14 consecutive wins and 9 title defenses, Silva holds the longest winning streak and title defense streak in UFC history.

Silva is ranked as the number one Middleweight in the world by multiple publications, and is the consensus No. 1 pound-for-pound fighter in the world according to ESPN, Sherdog, Yahoo! Sports, MMAFighting.com and other publications. UFC president Dana White has proclaimed Silva as "the greatest mixed martial artist ever."^{[undue weight? – discuss]} Silva is also the last Cage Rage Middleweight Champion and a former Shooto Middleweight Champion. Besides the UFC and Cage Rage, Silva has fought for a number of other MMA promotions including the Pride Fighting Championships, Shooto and Rumble on the Rock.

Although known primarily for his mastery of Muay Thai striking, Silva is also a Brazilian Jiu-Jitsu blackbelt, a rank he earned in 2006 from Antônio Rodrigo Nogueira who follows Gracie Lineage through Carlson Gracie, like Murilo Bustamante and the Brazilian Top Team. He began martial arts training at the age of 14, training Tae kwon do and earning a black belt by the age of 18. He is also a black belt in Judo and a yellow rope in Capoeira.

Chris Weidman (born June 17, 1984) is an American mixed martial artist and former collegiate wrestler. He is currently signed as a Middleweight with the UFC. Weidman attended Baldwin high school on Long Island where he was a Nassau County and New York State wrestling Champion. Weidman earned All-American wrestling honors at NCC before transferring to Hofstra where he became a Two-Time Division I All-American, placing 3rd at the NCAA tournament his senior year. Weidman graduated from Hofstra University with a Bachelor's Degree in Psychology.

Weidman trains and competes as part of the Serra-Longo Fight Team under the tutelage of Ray Longo and Matt Serra; Weidman currently competes in the middleweight division. In just his 3rd fight, Weidman fought a highly touted Uriah Hall for the Ring of Combat middleweight title in what was billed as a striker vs wrestler matchup; Weidman showed his striking prowess by knocking Hall out in dramatic fashion. Weidman qualified for and competed at the 2009 ADCC Submission Wrestling World Championship (with just 1 year of formal Jiu-Jitsu training) in Barcelona where he lost to world renowned Jiu-Jitsu practitioner André Galvão. As of 2010, multiple MMA ranking panels had Weidman ranked as high as the #1 ranked prospect in the world at 185 lbs. Weidman was also listed as the number one prospect in all of MMA in the 2011 Top 50 Prospects piece put out by MMARanked.com