This is a list of current and past undisputed champions of boxing.

At least since John L. Sullivan, in the late 19th century, there have been world boxing champions. The first of today's organizations to award a world title was the World Boxing Association, known as the National Boxing Association when it sanctioned its first title fight in 1921 between Jack Dempsey and Georges Carpentier for the heavyweight championship.

There are now four major sanctioning bodies in professional boxing. The official rules and regulations of the World Boxing Association,World Boxing Council,International Boxing Federation and World Boxing Organization all recognize the other three major sanctioning bodies in their rankings and title unification rules. Each of these organizations sanction and regulate championship bouts and award championships. American boxing magazine The Ring began awarding world championship belts in 1922.

There are seventeen weight divisions. To compete in a weight class, a boxer's weight must not exceed the upper limit. Manny Pacquiao has won world championships in eight different weight classes, more than any other boxer. The Klitschko brothers, Vitali and Wladimir, hold all five major titles in the heavyweight division. They are the first brothers to hold versions of the heavyweight championship at the same time.

Michael Gerard "Mike" Tyson (born June 30, 1966) is a retired American professional boxer. Tyson is a former undisputed heavyweight champion of the world and holds the record as the youngest boxer to win the WBC, WBA and IBF heavyweight titles at 20 years, 4 months and 22 days old. Tyson won his first 19 professional bouts by knockout, with 12 of them occurring in the first round. He won the WBC title in 1986 after defeating Trevor Berbick by a TKO in the second round. In 1987, Tyson added the WBA and IBF titles after defeating James Smith and Tony Tucker. He was the first heavyweight boxer to simultaneously hold the WBA, WBC and IBF titles, and the only heavyweight to individually unify them.

In 1988, Tyson became the lineal champion when he knocked out Michael Spinks in the first 91 seconds of the fight. Tyson successfully defended the world heavyweight championship nine times, including victories over Larry Holmes and Frank Bruno. Tyson lost his titles to 42-to-1 underdog James "Buster" Douglas on February 11, 1990, in Tokyo, Japan, by a knockout in round 10. Tyson continued in his quest to regain the titles, defeating Donovan Ruddock twice in 1991. Tyson was then scheduled to take on the undisputed heavyweight champion Evander Holyfield but pulled out due to injury.

Marvelous Marvin Hagler (born Marvin Nathaniel Hagler in Newark, New Jersey, May 23, 1954) is a retired American professional boxer who was Undisputed World Middleweight Champion from 1980 to 1987. Hagler made twelve undisputed title defenses and holds the highest KO% of all middleweight champions at 78%. At six years and seven months, his reign as undisputed middleweight champion is the second longest of the last century, behind only Tony Zale (although Zale was inactive for 4 years due to World War II). In 1982, annoyed that network announcers often did not refer to him by his nickname, "Marvelous," Hagler legally changed his name to Marvelous Marvin Hagler."

Hagler is an inductee of the International Boxing Hall of Fame and the World Boxing Hall of Fame. He was named Fighter of the Decade (1980s) by Boxing Illustrated and twice named Fighter of the Year by Ring Magazine and the Boxing Writers Association of America. In 2001 and 2004 the Ring named him the 4th greatest middleweight of all time and in 2002 named him the 17th-greatest fighter of the past 80 years. The International Boxing Research Organisation (IBRO) rates Hagler as the sixth-greatest middleweight of all time.Boxrec rates Hagler the fifth-best middleweight of all time. Many analysts and boxing writers consider Hagler to have one of the best "chins" in boxing history.

Sugar Ray Leonard (born May 17, 1956) is an American retired professional boxer and occasional actor. He was named Ray Charles Leonard, after his mother's favorite singer, Ray Charles. Leonard was the first boxer to earn more than $100 million in purses, won world titles in five weight divisions and defeated future fellow International Boxing Hall of Fame inductees Wilfred Benítez, Thomas Hearns, Roberto Durán and Marvin Hagler. Leonard was named "Boxer of the Decade" for the 1980s.

Leonard, the fifth of seven children, was born in Rocky Mount, North Carolina to Cicero and Getha Leonard. He grew up in Wilmington, N.C. When he was three, the family moved to Washington, D.C. When he was ten, they settled permanently in Palmer Park, Maryland. His father worked as a supermarket night manager, his mother was a nurse.

Leonard was a shy child, and aside from the time he nearly drowned in a creek during a Seat Pleasant flood, his childhood was uneventful. He stayed home a lot, reading comic books and playing with his dog. "He never did talk too much," his mother said. "We never could tell what he was thinking. But I never had any problems with him. I never had to go to school once because of him."