Cusae (Greek: Kusai) was a city in Upper Egypt, known to the Ancient Egyptians as Qis or Kis. Today, the town is known as El Qusiya, and is located on the west bank of the Nile in the Asyut Governorate.
At the beginning of the reign of the Theban pharaoh Kamose, Cusae marked the boundary between the northern Hyksos realm (the 15th Dynasty) and the southern Theban kingdom (the 17th Dynasty). It was a cult centre for Hathor, and also contained a necropolis, Meir, which was used during the Middle Kingdom to hold the tombs of local aristocrats.
During the 5th century, the city was the settlement of Legio II Flavia Constantia.
The bishopric of Cusae was a suffragan of the metropolitan see of Antinoë, capital of the Roman province of Thebaid I. Achilles (or Achilleus) was ordained bishop of the see by Meletius of Lycopolis. Another, Elias, was of the 4th or 5th centuries. Theonas took part in the Second Council of Constantinople (553). Later bishops took the non-Chalcedonian side, the first of them being Gregorius, who assisted Pope John II (III) of Alexandria on his deathbed.
- Grimal, Nicolas (1992). A History of Ancient Egypt. Oxford: Blackwell Books. p. 191.
- S. Timm, Das christlich-koptische Ägypten, Wiesbaden 1982-1992, 2181 e 2189 n. 4.
- Michel Lequien, Oriens christianus in quatuor Patriarchatus digestus, Paris 1740, Vol. II, coll. 595-598
- Raymond Janin, v. Cusae in Dictionnaire d'Histoire et de Géographie ecclésiastiques, vol. XIII, Paris 1956, col. 1117
- Klaas A. Worp, A Checklist of Bishops in Byzantine Egypt (A.D. 325 - c. 750), in Zeitschrift für Papyrologie und Epigraphik 100 (1994) 283-318
- Sophrone Pétridès, "Cusae" in Catholic Encyclopedia (New York 1908)
- Annuario Pontificio 2013 (Libreria Editrice Vaticana 2013 ISBN 978-88-209-9070-1), p. 878