Arianism

An early Christian heresy named after Arius (250-336 AD). He taught that Jesus was not in existence for all time, but was created by God near the end of the first century BC. The church at the time was evenly divided over whether Arianism was truth or a heresy. Constantine's vote swayed the balance, and it became a heresy.

Arius (sometimes spelled as Areius) also taught a form of monotheism in which there is only one person in the Godhead (the Father) and not a Trinity.