Leo I, also known as Leo the Great, was the Bishop of Rome from 440 until his death in 461. Born in Tuscany, he was a Roman aristocrat who played a crucial role in defining the central authority of the papacy by linking it to the succession of Saint Peter. He is widely recognized for his theological work, particularly his contributions to the Council of Chalcedon regarding the nature of Christ. His leadership during the fifth century helped shape the institutional structure of the early Church.