The Council of Constantinople refers to two significant ecumenical councils held in the city of Constantinople. The first, in 381 AD, aimed to address the Arian controversy and affirm the Nicene Creed, solidifying the doctrine of the Trinity. It was attended by bishops from various regions and resulted in the condemnation of Arianism, a belief that denied the full divinity of Christ. The second council, held in 553 AD, focused on the nature of Christ and the writings of certain theologians. It reaffirmed the decisions of the earlier councils and sought to maintain unity within the Christian Church, particularly against the backdrop of the growing influence of Nestorianism and Monophysitism.