The Chalcedonian Creed is a creed which was made during the Council of Chalcedon in the year 451. This council is one of the seven ecumenical councils. It is recognised by the Eastern Orthodox, the Catholics, and by many Protestant Churches. It is the first council the Oriental Orthodox Church does not recognize.
The Chalcedonian creed was written during a controversy between the Western and Eastern Churches. They could not agree about the meaning of Incarnation, the influence of the emperor in the church, and the role of the Roman Pope. The Western Churches had no problems accepting the creed, but some Eastern Churches had.
The creed became doctrine in the Orthodox Church. The Coptic church of Alexandria disagreed. They used Cyril's formula instead. They said that the creed should say that Christ be acknowledged "from two natures" rather than "in two natures".