The original Nicene Creed was first adopted at the First Council of Nicaea in 325. In 381, it was amended at the First Council of Constantinople. The amended form is also referred to as the Nicene Creed, or the Niceno-Constantinopolitan Creed for disambiguation.

The Nicene Creed is the defining statement of belief of Nicene or mainstream Christianity and in those Christian denominations that adhere to it. The Nicene Creed is part of the profession of faith required of those undertaking important functions within the Catholic Church.

Nicene Christianity regards Jesus as divine and co-eternal with God the Father. Various non-Nicene doctrines, beliefs, and creeds have been formed since the fourth century, all of which are considered heresies by adherents of Nicene Christianity.