John Powers Severin was born in Jersey City, New Jersey, and attended the High School of Music and Art in New York City, together with Harvey Kurtzman, Will Elder, Al Jaffee and Al Feldstein. He had published his first cartoons at the age of 10 in the the Hobo News in 1932. After serving in the Army, he entered the comic book field in 1947. He did his first work through Simon and Kirby's Crestwood studio. In cooperation with Bill Elder, who did the inking, he produced covers and stories for Prize Comics, including features called 'American Eagle', 'Lazo Kid' and 'Black Bull'. The pair also did many fillers and contributions to romance and crime titles by Better Publications, National Periodicals, and Timely.
In 1953, John Severin began working for EC Group, concentrating mainly on western and war comics, which were published in the titles Two-Fisted Tales and Frontline Combat. Later on he also was a regular on Harvey Kurtzman's early issues of the MAD comic book, and served as an editor of the final issues of Frontline Combat. Severin also worked on EC's New Direction title Extra!, for which he drew the 'Steve Rampart' feature.
After EC folded in 1955, Severin started drawing for Stan Lee's Atlas group, initially on westerns like 'Kid Colt', 'Rawhide Kid' and 'The Ringo Kid'. When Atlas became the Marvel group, Severin worked for the whole new range of comics, including 'The Hulk' and inking Dick Ayers's pencils on 'Sgt. Fury and His Howling Commandos'. He was the main artist for the MAD competitor Cracked, and freelanced for other companies in the 1960s. He drew 'Sgt. Rock' for DC, and contributed to James Warren's magazines Eerie, Creepy and Blazing Combat, and to titles published by Dell, Harvey and Charlton, often with a focus on western. He worked with his sister Marie Severin on the 'King Kull' title for Marvel in 1973. Still active until the 2000s, he has worked on titles like 'Desperadoes', 'Suicide Squad', 'American Century', 'Caper', 'The Punisher', 'Conan' and 'Bat Lash'. In 2003 he illustrated the controversial version of 'Rawhide Kid' mini-series, in which the classic western hero was a gay gunslinger.