Charles L. "Sonny" Liston (c. 1930 – December 30, 1970) was an American professional boxer who competed from 1953 to 1970. A dominant contender of his era, he became the world heavyweight champion in 1962 after knocking out Floyd Patterson in the first round, repeating the knockout the following year in defense of the title; in the latter fight he also became the inaugural WBC heavyweight champion. Liston was particularly known for his immense strength, formidable jab, long reach, toughness, and his infamously intimidating appearance.

Although Liston was widely regarded as unbeatable, he lost the title in 1964 to Muhammad Ali (then known as Cassius Clay), who entered as a 7–1 underdog. Liston retired in his corner due to an inflamed shoulder. Controversy followed with claims that Liston had been drinking heavily the night before the fight and had entered the bout with a lame shoulder. In his 1965 rematch with Ali, Liston suffered an unexpected first-round knockout that led to unresolved suspicions of a fix. He was still a world-ranked boxer when he died under mysterious circumstances in 1970. Underworld connections and his unrecorded dates of birth and death added to the enigma.

The Ring magazine ranks Liston as the tenth greatest heavyweight of all time, while boxing writer Herb Goldman ranked him second and Richard O'Brien, Senior Editor of Sports Illustrated, placed him third. Alfie Potts Harmer in The Sportster also ranked him the third greatest heavyweight and the sixth greatest boxer at any weight. Liston was inducted into the International Boxing Hall of Fame in 1991.