The Arian controversy was a significant theological dispute in the early Christian church during the 4th century. It centered around the teachings of Arius, a priest from Alexandria, who argued that Jesus Christ was not co-eternal with God the Father and was instead a created being. This belief challenged the traditional understanding of the Trinity, leading to widespread debate and division among Christians. The controversy reached a peak at the First Council of Nicaea in 325 AD, where church leaders gathered to address these issues. The council ultimately rejected Arius's views, affirming that Jesus is "of the same substance" as God the Father, which laid the foundation for the orthodox Christian belief in the Trinity.