Robber Council of 869-870
The Robber Council of 869-870 was a council held in Constantinople called by Emperor Basil I the Macedonian and Adrian II of Rome, meeting from October 5, 869 to February 28, 870. It deposed and condemned St. Photius the Great as patriarch and, of the four Eastern patriarchates, ranked Constantinople before Alexandria, Antioch, and Jerusalem.
The acts of this council were eventually abrogated at the Eighth Ecumenical Council, held in Constantinople in 879-880. This latter council was held to be ecumenical by both East and West until the 11th century, when Rome repudiated the council of 879-880 and retroactively regarded the council of 869-870 to be the Eighth Ecumenical Council, but which the Orthodox Church continues to regard as a robber council.