Christian bishop and missionary who evangelized the Goths, reputedly created the Gothic alphabet, and wrote the earliest translation of the Bible into a Germanic language. Although his life cannot be reconstructed with certainty, fragments have come from 4th- and 5th-century ecclesiastical historians.

Ulfilas is believed to have descended from 3rd-century Cappadocians, who, captured by the Goths, were displaced and settled north of the Danube River. At the age of 30 he was supposedly sent on an embassy to the Roman emperor and was consecrated (341) bishop of the Gothic Christians by Eusebius of Nicomedia, bishop of Constantinople, an Arian (i.e., a follower of the heretical doctrine that the Son was neither equal with God the Father nor eternal). Because of persecution by the Gothic ruler, Ulfilas, after working for seven years among the Goths north of the Danube, led his congregation to Moesia (now part of Bulgaria) with the consent of the Arian Roman emperor Constantius II. Some historians report that Ulfilas in about 375 helped the persecuted Christian Goths to cross the Danube into Roman territory.

By the time of his consecration, Ulfilas had accepted the homoean formula (i.e., the Trinitarian doctrine affirming that the Son was “like” the Father) promulgated by the Council of Constantinople (360), which he attended. He subsequently taught the similarity of the Son to the Father and the complete subordination of the Holy Spirit, an Arian form of Christianity that he carried to the Visigoths. He was certainly the principal agent in their conversion, a fact of great significance for the history of the Christian church and of Europe. When in 379 a champion of Nicene orthodoxy, Theodosius I the Great, became Roman emperor, Ulfilas apparently led a party of compromise and conciliation with the Homoean position. After the Council of Aquileia (381), Theodosius summoned Ulfilas to Constantinople for discussions, during which he died.

Ulfilas' outstanding contribution to writing is his invention of the Gothic alphabet, which he devised from Greek (primarily) and Latin. For the first time in the Germanic world, writing could be used for the propagation of ideas. He coined a Germanic Christian terminology, some of which is still in use. Before 381 he translated parts of the Bible from Greek to Gothic. Much of his Gothic translations of the Gospels and Pauline Letters survive, together with fragments of his Book of Nehemiah. Although he reputedly translated the whole Bible except the Books of Kings, the extent of his work cannot be ascertained. Surviving passages from his Bible translation are in W. Streitberg's Gotische Bibel (3rd ed., 1950). He reportedly wrote many sermons and interpretations in Gothic, Greek, and Latin, and some extant Arian writings have been ascribed to him.

The national Gothic church that Ulfilas helped to create, endowing it with a vernacular Bible and probably liturgy, was Arian from the start. The Goths' adherence to Arianism caused a breach between them and the Roman Empire that made Arianism part of the national self-consciousness of the Visigoths and of other Germanic peoples, including Ostrogoths, Vandals, and Burgundians.