Middleweight is a division, or weight class, in boxing. Early boxing history is less than exact, but the middleweight designation seems to have begun in the 1840s. In the bare-knuckle era, the first middleweight championship fight was between Tom Chandler and Dooney Harris in 1867. Chandler won, becoming known as the American middleweight champion.

The first middleweight fight with gloves may have been between George Fulljames and Jack (Nonpareil) Dempsey (no relation to the more famous heavyweight of the same name). Dempsey knocked out Fulljames on July 30, 1884.

In the modern era, middleweight means that the fighter's official weight does not exceed 160 pounds (72.64 kg). (In practice, however, since weigh-ins take place usually 24 hours before the actual fight, many fighters show up at the actual ringside weighing more.)

The current middleweight champion, Kelly Pavlik, won a T.K.O. victory in September 2007, defeating the defending champion, Jermain Taylor in the 7th round.

Some notable middleweights have been:

• Arthur Abraham
• Fred Apostoli
• Nigel Benn, 27 KO's from 31 middleweight contests, won WBO version of title and WBC title at super-middle
• Nino Benvenuti, world champion in 1967 and again from 1968 to 1970.
• Marcel Cerdan, the first non-American to win a world middleweight title.
• Billy Conn
• Oscar De La Hoya
• Roberto Duran, The "Hands of Stone" defeated Iran Barkley for the WBC middleweight championship.
• Chris Eubank unbeaten in 28 middleweight contests, held WBO title at middle and super-middle, beat Benn.
• Bob Fitzsimmons, who was the first fighter - there have only been a handful since - to hold titles in three of the original eight divisions, and the first middleweight champion to capture the heavyweight title
• Gene Fullmer
• Ceferino Garcia
• Rocky Graziano
• Harry Greb
• Emile Griffith
• "Marvelous" Marvin Hagler, defended his title 12 times, first middleweight champion to hold top three sanctioning body belts.
• Tommy "The Hitman" Hearns, defeated Juan Roldan for the WBC middleweight championship.
• Bernard Hopkins, defended his title a record 20 times, first fighter in history to unify the WBO, WBC, IBF and WBA titles
• Roy Jones Jr., won the IBF version of the belt
• Stanley Ketchel
• Jake "Raging Bull" LaMotta
• Sugar Ray Leonard
• Gerald McClellan, ferocious puncher, held WBO and WBC middleweight titles, paralysed fighting Benn
• Al McCoy
• Carlos Monzon, who unified the title and defended it 14 times
• Da'Shayne Pace
• Sugar Ray Robinson, held the title a record five times. Widely considered greatest pound-for-pound boxer ever.
• Freddie Steele
• Felix Trinidad
• Mickey Walker
• Tony Zale