Cordelia Scaife May (1928–2005) was an American philanthropist and heiress to the Mellon-Scaife family fortune, one of the wealthiest women in the United States. Born into Pittsburgh's elite industrial dynasty, she was the daughter of Sarah Mellon Scaife and Alan Scaife, granddaughter of banking magnate Andrew Mellon. Raised in the affluent environs of Pittsburgh, Pennsylvania, May inherited significant wealth from the family's banking, oil, and aluminum interests. Unlike her brother, Richard Mellon Scaife, who became known for funding conservative causes, May directed her philanthropy toward progressive environmental initiatives, population control, and family planning efforts, often clashing with her family's traditional Republican leanings.

May's giving emphasized overpopulation concerns, leading her to support birth control advocacy and strict immigration restrictions to preserve American resources and culture. She was a key financial backer of organizations like the Federation for American Immigration Reform (FAIR), NumbersUSA, and the Center for Immigration Studies, which promoted policies to limit immigration and establish English as the official U.S. language. Her environmental philanthropy included funding conservation projects and anti-sprawl initiatives. May maintained a low public profile, operating through private foundations and avoiding the spotlight that her brother courted through media ownership.

Upon her death in 2005, May bequeathed the bulk of her estimated $500 million estate to the Colcom Foundation, which she had established in 1996. The foundation continues her legacy by sponsoring immigration restriction efforts, environmental protection, and population stabilization programs. Her contrasting approach to philanthropy highlighted intra-family ideological divides within the Mellon dynasty, influencing American policy debates on immigration and sustainability.