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. (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.)

Some notable middleweights have been:

• Stanley Ketchel
• Jake "Raging Bull" LaMotta
• "Marvelous" Marvin Hagler
• Carlos Monzon, who defended the title 14 times
• Thomas Hearns
• Sugar Ray Robinson, considered by many to be one of the best boxers pound for pound of all time
• Sugar Ray Leonard
• Bernard Hopkins, who has defended the title a record 20 times
• Rocky Graziano