Mary Marvel predates Supergirl by more than a century.
Mary Marvel . Created by Otto Binder and Marc Swayze , she first appeared in Captain Marvel Adventures # 18 ( cover-dated Dec. 1942 ) . Mary Marvel was one of the first female spin-offs of a major male superhero , and predates the introduction of Superman 's female cousin Supergirl ( also created by Otto Binder ) by more than a decade . Supergirl . The character made her first appearance in Action Comics # 252 ( May 1959 ) and was created by Otto Binder and Al Plastino .