In Greek mythology, Sidero (Σιδηρώ "the Iron One") was the second wife of Salmoneus and stepmother of the twins Pelias and Neleus. She mistreated the twins' mother Tyro horribly, incurring their wrath when they reached adulthood. Although Sidero fled from them into Hera's district, Pelias nevertheless murdered her atop the altar to Hera.