Pope Sixtus III

[1][2] Sixtus was born in Rome and before his accession he was prominent among the Roman clergy,[1] and frequently corresponded with Augustine of Hippo.

[3] According to Peter Brown, before being made pope, Sixtus was a patron of Pelagius, who was later condemned as a heretic,[4] although Alban Butler disagrees and attributes the charge to Garnier.

He also defended the rights of the pope over Illyria and the position of the archbishop of Thessalonica as head of the local Illyrian church against the ambition of Proclus of Constantinople.

He built the Liberian Basilica as Santa Maria Maggiore, whose dedication to Mary the Mother of God reflected his acceptance of the Ecumenical council of Ephesus which closed in 431.

The council gave her the Greek title Theotokos (literally "God-bearer", or "Mother of God"), and the dedication of the large church in Rome is a response to that.