The Arian Baptistry in Ravenna, Italy is a Christian baptismal building that was erected by the Ostrogothic King Theodoric the Great between the end of the 5th century and the beginning of the 6th century A.D., at the same time as the Basilica of Sant' Apollinare Nuovo.

Ravenna is the capital city of the Province of Ravenna, in the Emilia-Romagna region of Northern Italy. It was the capital city of the Western Roman Empire during the 5th century until its collapse in 476, after which it served as the capital of the Ostrogothic Kingdom and then the Byzantine Exarchate of Ravenna.