Cecropius was the name of two early Christian bishops:
1. OF NICOMEDIA, in Bithynia, a Semi-arian, who was transferred from Laodicea by Constantius in 351. Athanasius (Contra Arian. p. 290) charges him with having secured his elevation by his calumnies and plots against the orthodox. In the year of his appointment to Nicomedia he attended the synod at Sirmium, and took part in the deposition of Photinus (Athan. Epis. ad Solit. p. 800). Cecropius was one of the bishops who attended the consecration of the church erected at Anevra, in 358, by Basil, to whom a letter was addressed by George of Laodicea, representing the danger the faith was exposed to; in consequence of the recognition of Astius and his disciples at Antioch by Eudoxius, and urging them to take bold measures for their deposition (Sozomen, H.E. 4, 13). A deputation was accordingly sent to Constantius, who ordered that Aitius and some of his followers should be brought before Cecropius to answer to the charges alleged against them (ibid.4. 24). Cecropius perished in the earthquake which devastated Nicomedia in 358, and prevented the proposed council from being held there.
2. OF SEBASTOPOLIS, took a leading part in the Council of Chalcedon in 451. At the second session, Oct. 10, Cecropius strenuously opposed the formation of any new definition of the faith, and required that the Nicene creed and the letter of pope Leo to Flavian should be read for the acceptance of the assembled fathers. He was one of the deputation sent to serve the second 'citation on Dioscorus and refused to accept his plea of illness as a reason for declining to attend. At the fifth session he vehemently urged that all present should sign the definition of faith then presented, or leave the council (Labbe, Concil. 4, 338 sq.).