Gene Fullmer (b. July 21, 1931) was a strong, brawling American middleweight boxer. Fullmer won the world middleweight championship on January 2, 1957 when he upset the legendary Sugar Ray Robinson by winning a 15 round decision.

On May 1, 1957 Fullmer and Robinson fought a storied rematch. The fight began as expected with Fullmer using his strength, and awkwardness to bull into Robinson and force him onto his heels. In the 5th round Robinson, while backing up, lashed out with what has been called the perfect left hook. It caught Fullmer flush on the chin and knocked him cold.

In 1959, the National Boxing Association withdrew its recognition of Robinson as middleweight champion. Fullmer, and fellow former middleweight champion Carmen Basilio fought for the vacant NBA title on August 28, 1959, and Fullmer won the crown when he TKOed Basilio in the 14th round. Meanwhile, Robinson was to lose his version of the middleweight championship to Paul Pender .

Fullmer and Pender never met to settle their claims to the middleweight title and Pender eventually retired. Meanwhile Fullmer fought and turned back the challenges of many top contenders, such as Basilio, Robinson, Spider Webb, Florentino Fernandez and welterweight champion Benny "Kid" Paret. He also narrowly escaped being dethroned when he was held to 15 round draws by Robinson and future titleholder Joey Giardello.

Fullmer finally lost the middleweight title to Dick Tiger on October 23, 1962 on a unanimous decision. They fought a rematch on February 23, 1963, which resulted in a draw. Fullmer's attempts to regain the middleweight crown finally ended when he was TKOed in 7 rounds by Tiger on August 10, 1963.

Fullmer's final record included 55 wins (24 by KO), 6 losses and 3 draws.