Pope St. Leo the Great

Pope from 440, Leo wrote the famous Tome — read at the Council of Chalcedon in 451 — that defined the orthodox doctrine of the two natures of Christ. He met Attila the Hun outside Rome in 452 and persuaded him to turn back, and personally negotiated with Genseric the Vandal three years later. The first pope to be called "the Great" by acclamation.

Before his pontificate, Leo served as a deacon and diplomat, mediating quarrels among bishops in Gaul. As pope he asserted the primacy of the Roman See with a clarity that shaped the papacy for centuries, insisting that Peter speaks through every successor who sits in his chair.

His sermons — nearly a hundred survive — are masterpieces of Latin prose: precise, warm, and doctrinally luminous. He died in 461 having guided the Church through the collapse of the Western Empire, and was declared a Doctor of the Church in 1754. His feast is kept on November 10.