Pope Leo I (c. 400 – 10 November 461), also known as Saint Leo the Great, was Pope from 440 to his death in 461.

He was a Roman aristocrat, and was the first pope to have been called "the Great". He is perhaps best known for having met Attila the Hun in 452 and persuading him to turn back from his invasion of Italy. 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 Ecumenical Council of Chalcedon.