The smallest professional weight class. Recognised by the WBC and WBO from 1987 and the WBA / IBF shortly thereafter, the 105-pound limit is fought almost exclusively by Latin American and East-Asian fighters. The most decorated minimumweight in history is Mexico's Ricardo López, who retired in 2002 with a 51-0-1 record and the only undefeated reign of more than ten years in modern boxing.

Created in 1975 by both the WBA and WBC, light flyweight (108 lb) is the home of the first below-flyweight pay-per-view headliner: Michael Carbajal vs. Humberto González (1993), the first sub-115-pound fight to gross more than $1 million for each combatant. Currently dominated by Japan's Kenshiro Teraji, who unified the division in 2023.

Boxing's oldest 'small' division, fought to a flyweight limit since 1909. Long dominated by Mexican and Thai fighters, the 112-pound class has produced four of the longest-reigning champions in history (Pascual Pérez 1954-60, Pongsaklek Wonjongkam 2001-07/2010-12, Miguel Canto 1975-79, Sot Chitalada 1984-91).

The 115-pound super-flyweight division (also called junior bantamweight by the IBF) is the spiritual home of the post-2010 little-man golden age. Thailand's Khaosai Galaxy held the WBA title for 7 years (19 defences) in the 80s. In the 2010s the division was reshaped by the Roman Gonzalez–Srisaket Sor Rungvisai–Juan Francisco Estrada–Jesse Rodríguez quadrangle.

Bantamweight (118 lb) sits at the upper end of the 'sub-featherweight' classes and has historically been dominated by Latin American and East Asian fighters. The division was held undisputed by Japan's Naoya Inoue from 2022 to 2023 — the first undisputed bantamweight reign of the four-belt era — and is currently the cleanest contender ladder in the sport thanks to Inoue, Junto Nakatani, and the unified bantam champions all coming up via the WBSS tournaments.

A relatively young division (created by the WBC in 1976), super bantamweight (122 lb) is currently held undisputed by Naoya Inoue, who unified the four belts in 2023 in the same calendar year he had become undisputed at bantamweight. The four-Mexican brawl-pit era of Barrera–Morales–Márquez–Vázquez in the 2000s gave the division a brutal, fan-friendly reputation it still trades on.

A classical division (created 1889), featherweight at 126 lb has produced more pound-for-pound elites than almost any other class. The 1948-1958 Willie Pep / Sandy Saddler four-fight rivalry is one of the great trilogies in the sport. In the 1980s Eusebio Pedroza held the WBA title for 7 years; in the 2000s Marco Antonio Barrera, Erik Morales, and Manny Pacquiao formed a four-way pound-for-pound knot at the weight.

Created in 1921 as the "junior lightweight" division, super featherweight (130 lb) is one of boxing's pound-for-pound goldmines. The division has crowned Floyd Mayweather (1998), Manny Pacquiao (briefly), Vasiliy Lomachenko (2014), and Gervonta Davis (2018-21). Currently a four-belt knot with Emanuel Navarrete, O'Shaquie Foster, and Lamont Roach all holding straps.

One of the original eight weight classes (1909), lightweight at 135 lb is fighting royalty. Roberto Durán — undefeated for the first 13 years of his pro career — is widely considered the greatest lightweight in history. The division produced Pernell Whitaker (one of the best pure boxers of all time), Julio César Chávez, Vasiliy Lomachenko, and currently the four-way unification contender pool of Davis, Stevenson, Haney, and the now-passed-through Tank–Ryan Garcia era.

Created in 1959 by Box of Joy, the 140-pound division is the natural home of fighters who outgrow lightweight but who would be small at welterweight. Aaron Pryor's 1980s reign is generally considered the GOAT performance at the weight; Terence Crawford and Josh Taylor were both undisputed champions in the four-belt era (Crawford 2017, Taylor 2021).

The glamour division. Welterweight at 147 lb has produced more all-time top-10 pound-for-pound entries than any other class — Sugar Ray Robinson, Henry Armstrong, Sugar Ray Leonard, Thomas Hearns, Pernell Whitaker, Floyd Mayweather, Manny Pacquiao, and now Terence Crawford have all held versions of the welterweight title. The 2023 Crawford-Spence unification was the first undisputed welterweight bout since Robinson in the 1940s.

The first "junior" division to be sanctioned (WBA, 1962). Super welterweight (154 lb) is currently structured around the 6'5" reach of Sebastian Fundora — the tallest world champion in modern boxing — and the breakout star Xander Zayas. The class is best remembered, though, for the 1980s Hearns–McCallum–Norris–Curry quartet and the 2000s Trinidad–De La Hoya–Mayweather–Mosley quadrangle.

The original 'middle' class (1884). Middleweight is the only division apart from heavyweight to have had three different fighters reign for 7+ years (Carlos Monzón 1970-77, Bernard Hopkins 2001-05, Gennady Golovkin 2014-18). In 2018 Canelo Álvarez became the first Mexican to win the lineal middleweight title since Marco Antonio Rubio in 2012.

The newest of the major classical divisions, super middleweight (168 lb) was created by the IBF in 1984. Joe Calzaghe held the WBO title for over 10 years (21 defences). Andre Ward retired undefeated as undisputed super middleweight champion in 2017 after winning the Super Six tournament. Canelo Álvarez became the first four-belt undisputed super middleweight champion in November 2021.

Boxing's most underrated weight class for top-end skill: light heavyweight (175 lb) has crowned only seven undisputed four-belt champions in the modern era, the most recent being Artur Beterbiev in January 2024. Archie Moore made 21 successful 175 defences from 1952 to 1962, an absolute record. The division has produced Bob Foster, Michael Spinks, Roy Jones Jr., and now the Beterbiev-Bivol-Benavidez triangle.

Created in 1979 (WBC) to bridge the gap between 175-pound light heavies and increasingly large heavyweights, cruiserweight (200 lb) was undisputed only twice in its history: once by Evander Holyfield in 1988 (he immediately moved up) and once by Oleksandr Usyk in 2018, winning the World Boxing Super Series final against Murat Gassiev. The current era is shaped by Australia's Jai Opetaia and the surprise return of Gilberto Ramírez.

The marquee division. Heavyweight has no upper weight limit (the WBC introduced a 224-pound "bridgerweight" class below it in 2020). The four-belt era of heavyweight unification was opened in 1999 when Lennox Lewis became undisputed champion. In May 2024 Oleksandr Usyk became the first undisputed four-belt heavyweight champion of the modern era by outpointing Tyson Fury.