Arianism is a Christian belief asserting that Jesus Christ is the Son of God who was created by God the Father at a point in time, and is therefore subordinate to the Father. Arian teachings were first attributed to Arius (c. AD 250–336), a Christian presbyter in Alexandria, Egypt. The teachings of Arius and his supporters opposed the prevailing theological views held by proto-orthodox Christians, regarding the nature of the Trinity and the nature of Christ. The Arian concept of Christ is that the Son of God did not always exist, but was created by God the Father.

The Ecumenical First Council of Nicaea of 325 deemed it to be a heresy. Arius was pronounced a heretic at the Ecumenical First Council of Constantinople of 381.

The Roman Emperors Constantius II (337–361) and Valens (364–378) were Arians or Semi-Arians, as were the first King of Italy, Odoacer (433?–493), the Goths, the Vandals, the Alamanni, and the Lombards until the 7th century.

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