William Burnside, PhD, also known as the Captain America of the 1950s, Commie Smasher or Bad Cap, is a fictional character appearing in American comic books published by Marvel Comics. He was created by writer Steve Englehart and artist Sal Buscema in Captain America #153–156 as an explanation for the reappearance of Captain America and Bucky in 1953 in Young Men comics and their subsequent adventures in the 1950s. It established through retroactive continuity that the character was a completely different one from the original Captain America, who was firmly established in The Avengers #4 as disappearing near the end of World War II. Since this revelation, the character serves as a foil personality to his predecessor, as a reactionary bigot driven violently insane by a flawed and incomplete copy of Project Rebirth's body enhancement treatment.

Steve Englehart is an American writer of comic books and novels. He is best known for his work at Marvel Comics and DC Comics in the 1970s and 1980s. His pseudonyms have included John Harkness and Cliff Garnett.