Isabel Martínez de Perón (Spanish pronunciation: [isaˈβel maɾˈtinez de peˈɾon], born María Estela Martínez Cartas, 4 February 1931), also known as Isabelita, is an Argentine politician who served as President of Argentina from 1974 to 1976. She was the first female republican head of state in the world, although other nations had female regnant monarchs or female heads of government.

Isabel Perón was the third wife of President Juan Perón. During her husband's third term as president from 1973 to 1974, she served as both Vice President and First Lady of Argentina. Following her husband's death in office in 1974, she served as President for almost two years before the military took over the government. Perón was then placed under house arrest for five years before she was exiled to Spain in 1981.In 2007 an Argentine judge ordered Perón's arrest over the forced disappearance of an activist in February 1976, on the grounds that the disappearance was authorized by her signing of decrees allowing Argentina's armed forces to take action against "subversives". She was arrested near her home in Spain on 12 January 2007. Spanish courts subsequently refused her extradition to Argentina.Since the death of Carlos Menem on 14 February 2021, Perón is the oldest living former Argentine president.