Mary Marvel, created by Otto Binder and Marc Swayze, first appeared in Captain Marvel Adventures #18 (December 1942), published by Fawcett Comics. Originally introduced as Mary Batson, the long-lost twin sister of Billy Batson (Captain Marvel), she discovers her ability to transform into a superpowered adult form by uttering the magic word "Shazam." Her powers, derived from a pantheon of goddesses—initially including Selena (grace), Hippolyta (strength), Ariadne (skill), Zephyrus (fleetness), Aurora (beauty), and Minerva (wisdom)—grant her superhuman strength, speed, flight, invulnerability, and wisdom, mirroring yet distinct from her brother's abilities. During the Golden Age, Mary starred in her own solo series, Mary Marvel (1945–1948), and became a core member of the Marvel Family alongside Captain Marvel and Captain Marvel Jr., establishing her as one of the earliest prominent female superheroes in comics.
Following Fawcett's cessation of superhero publications in 1953 due to legal disputes, DC Comics licensed and later acquired the characters, reviving them in the 1970s Shazam! series. After the Crisis on Infinite Earths (1985), Mary was reintroduced in The Power of Shazam! graphic novel and series (1994–1999), with a revised origin emphasizing her adoption by the wealthy Bromfield family and reunion with Billy. In the 2000s, particularly in Trials of Shazam! (2006–2008) and Countdown (2007–2008), she underwent dramatic developments, including the loss of her original powers after the Wizard's death, temporary acquisition of Black Adam's darker abilities leading to a corrupted "Black Mary" phase, possession by Desaad as a Female Fury, and eventual redemption.
In the New 52 reboot (2011), Mary Bromfield was reimagined as Billy Batson's foster sister rather than biological twin, debuting in Justice League (vol. 2) #8 (2012) as part of an expanded Shazam Family of foster siblings sharing powers. The Rebirth era and subsequent continuities retained this foster dynamic, with Mary serving as the responsible eldest sibling. Recent developments, including events in Lazarus Planet (2023) and The New Champion of Shazam! miniseries, saw her gain independent powers from female deities, briefly assume the primary champion role, reclaim the Mary Marvel moniker, and balance heroic duties with guardianship of her siblings and college studies.