Leo I

Pope Leo I (Italian: Leone I) (c. 391 – 10 November 461), also known as Leo the Great (Latin: Leo Magnus; Italian: Leone Magno), was Bishop of Rome from 29 September 440 until his death on 10 November 461. He is the first of the three Popes listed in the Annuario Pontificio with the title "the Great", alongside Popes Gregory I and Nicholas I.

Leo was a Roman aristocrat. He is perhaps best known for meeting Attila the Hun in 452 and persuading him to turn back from his invasion of Italy, though how large a part his personal authority played is debated, and some argue that Attila was already ready to end his campaign. He is also a Doctor of the Church, most remembered theologically for issuing the Tome of Leo, a document which was a major foundation to the debates of the Council of Chalcedon, the fourth ecumenical council. That meeting dealt primarily with Christology and elucidated the definition of Christ's being as the hypostatic union of two natures, divine and human, united in one person, "with neither confusion nor division". It was followed by a major schism associated with Monophysitism, Miaphysitism and Dyophysitism. He also contributed significantly to developing ideas of papal authority.