The First Council of Constantinople is recognized as the Second Ecumenical Council by the Assyrian Church of the East

Assyrian Church of the East

The Assyrian Church of the East, officially the Holy Apostolic Catholic Assyrian Church of the East ʻIttā Qaddishtā w-Shlikhāitā Qattoliqi d-Madnĕkhā d-Āturāyē), is a Syriac Church historically centered in Mesopotamia. It is one of the churches that claim continuity with the historical...

, the Oriental Orthodox, the Eastern Orthodox, the Roman Catholics, the Old Catholics, and a number of other Western Christian groups. It was the first Ecumenical Council

First seven Ecumenical Councils

In the history of Christianity, the first seven Ecumenical Councils, from the First Council of Nicaea to the Second Council of Nicaea , represent an attempt to reach an orthodox consensus and to establish a unified Christendom as the State church of the Roman Empire...

 held in Constantinople

Constantinople

Constantinople was the capital of the Roman, Eastern Roman, Byzantine, Latin, and Ottoman Empires. Throughout most of the Middle Ages, Constantinople was Europe's largest and wealthiest city.-Names:...

 and was called by Theodosius I

Theodosius I

Theodosius I , also known as Theodosius the Great, was Roman Emperor from 379 to 395. Theodosius was the last emperor to rule over both the eastern and the western halves of the Roman Empire. During his reign, the Goths secured control of Illyricum after the Gothic War, establishing their homeland...

 in 381. The council confirmed the Nicene Creed

Nicene Creed

The Nicene Creed is the creed or profession of faith that is most widely used in Christian liturgy. It is called Nicene because, in its original form, it was adopted in the city of Nicaea by the first ecumenical council, which met there in the year 325.The Nicene Creed has been normative to the...

 and dealt with other matters such as the Arian controversy

Arian controversy

The Arian controversy describes several controversies between the Christian Church fathers Arius and Athanasius related to Christology which divided the Christian church from before the Council of Nicaea in 325 to after the Council of Constantinople in 381...

 as it met in the church of Hagia Irene

Hagia Irene

Hagia Irene or Hagia Eirene , often erroneously rendered in English as St Irene, is a former Eastern Orthodox church located in the outer courtyard of Topkapı Palace in Istanbul, Turkey. It is open as a museum every day except Monday but requires special permission for admission.-Church:The...

 from May to July 381.

Pope Damasus I

Pope Damasus I

Pope Saint Damasus I was the bishop of Rome from 366 to 384.He was born around 305, probably near the city of Idanha-a-Velha , in what is present-day Portugal, then part of the Western Roman Empire...

 either was not invited or declined to attend, so this council is sometimes called the "unecumenical" council.