The Nicene Creed was issued by the Council of Nicaea, which met in A.D. 325 to address the debate between Alexander, bishop of Alexandria, and Arius, one of his elders.
Read further for an introduction, or jump directly to its text below.
For a fuller version of this, go to The Council of Nicea.
Arius had been excommunicated by Alexander for teaching that Jesus Christ was created by God in the beginning from nothing, in much the same way that God had created all other creatures. This view is currently held by the Jehovah's Witnesses, but it was brand new in A.D. 318.
It was offensive enough a belief that Alexander was urged by other church leaders to take appropriate action against Arius, who was quite unrepentant about believing something that went against the church in Alexandria and its bishop. Thus Arius was excommunicated.
This didn't stop Arius, who found a supporter in the bishop Eusebius of Nicomedia (not to be confused with Eusebius the historian, bishop of Caesarea). Arius not only had Eusebius on his side, but he taught his doctrine to traders and children, even composing jingles, and spread it throughout the eastern empire.
Fearful that the controversy would divide his empire, Constantine the Great assembled a council at Nicaea, in modern Turkey, to address the matter. This council condemned Arius and Eusebius (of Nicomedia) and composed the Nicene Creed as a statement of the historic doctrine of the Church.
The Nicene Creed teaches a doctrine that is mostly forgotten, despite its being quoted in many churches every week (usually in the form of the very similar Apostles Creed).
Our modern "orthodox" view of the Trinity is quite close to the Nicene Creed, but the beginning—"There is one God, the Father Almighty"—makes it clear that there are some differences.
There were between 250 and 318 bishops at the Council of Nicaea—depending on whose estimate you accept—and all but two assented to the Creed. The two were banned from the empire, but later repented.
Arius, too, who could not be at Nicaea because he was not a bishop, was banished from the empire at Nicea. He later died after Constantine sent him to Alexandria to seek reconciliation. There is much speculation that there was foul play involved.
Do take note of the use of the words "substance" and "consubstantial" in the Nicene Creed. They concern the Greek words ousios and homoousios, which was the main subject of the Arian controversy.
Text of the Nicene Creed as given by the council taken from The Ecclesiastical History of Socrates Scholasticus, Book 1 and ch. VIII, written circa AD 450. The creed has been added to since.