Saint Leo I

Pope Leo I, also known as Leo the Great (c. 391 – 10 November 461), was a Roman aristocrat who served as Bishop of Rome from 29 September 440 until his death on 10 November 461. He is renowned for his meeting with Attila the Hun in 452, where he persuaded the Hunnic leader to turn back from invading Italy. While his personal authority played a role, some debate how significant it was compared to other factors influencing Attila's decision. Leo is also recognized as one of the three Popes listed in the Annuario Pontificio with the title 'the Great,' alongside Popes Gregory I and Nicholas I. He is a Doctor of the Church, most remembered for issuing the Tome of Leo, which contributed significantly to the debates at the Council of Chalcedon.

This council dealt primarily with Christology and clarified the definition of Christ's being as the hypostatic union of two natures, divine and human, united in one person. His contributions also included developing ideas of papal authority. He is venerated for his role in Christian theology and ecclesiastical leadership.