Christian Arianism is a heretical theological belief that emerged in the fourth century and was named after Arius, a Christian priest in Alexandria, Egypt. Arius taught that the Son of God, Jesus Christ, was not co-eternal with the Father, but was instead a created being, distinct from the Father and subordinate to him. This belief was opposed by the orthodox Christian Church, which maintained that Jesus was fully divine and co-equal with the Father.
The Arian controversy caused significant division within the early Christian Church and led to the First Council of Nicaea in 325 AD, which condemned Arianism and affirmed the orthodox view of the Trinity. However, Arianism continued to persist and was adopted by various Germanic tribes in the early Middle Ages. The Visigoths, for example, converted to Arian Christianity and ruled over Spain until the seventh century.
Today, Arianism is considered a heresy by the mainstream Christian Church and is not a commonly held belief among Christians.