Spider-Girl is a fictional superheroine in Marvel Comics' MC2 universe. The character was created by Tom DeFalco and Ron Frenz as the teenage daughter of Peter Parker and Mary Jane Watson, and first appeared in What If #105.

May "Mayday" Parker is the child of Peter and Mary Jane Parker in a future, alternate universe continuity. Peter and Mary Jane named their daughter after his Aunt May. In the MC2 continuity, they were reunited with their baby daughter by Kaine, who found the child living with Alison Mongraine, the con artist who had kidnapped the baby on instruction from the Green Goblin. After they were reunited, Peter lost a leg during the horrific final conflict with the Green Goblin. After the battle Peter was offered a bionic replacement from Mister Fantastic but, considering it a wake-up call, decided to retire and focus on being a husband and father (the battle is glimpsed in Spider Girl #7, and fully explained in Spider Girl #49). For years, they chose to keep their past from May and hoped that she wouldn't develop powers of her own. Despite her parents' hopes, May began developing versions of her father's spider-powers when she was 15. At the same time, Normie Osborn, grandson of the original Green Goblin, set out to restore the family name. May donned Ben Reilly's Spider-Man costume to stop him and soon took to crime-fighting, at first hindered, then helped, by her worried parents.