Heraclea Cybistra (Greek: Hράκλεια Κύβιστρα; near modern Ereğli in Konya Province, Turkey), under the name Cybistra, had some importance in Hellenistic times owing to its position near the point where the road to the Cilician Gates enters the hills. It lay in the way of armies and was more than once sacked by the Arab invaders of Asia Minor (by Harun al-Rashid in 806 and al-Ma'mun in 832). Three hours’ ride south is the famous "Hittite" rock relief of a lynx, representing a king (probably of neighbouring Tyana) adoring a god. This was the first "Hittite" monument discovered in modern times (early 18th century, by the Swede Otter, an emissary of Louis XIV).
Cybistra was from an early stage a Christian bishopric, as shown by the participation of its bishop Timotheus in the First Council of Nicaea in 325. Cyrus took part in the Council of Chalcedon in 351 and was a signatory of the letter that the bishops of the Roman province of Cappadocia Secunda, to which Cybistra belonged, sent in 458 to Byzantine Emperor Leo I the Thracian after the murder of Proterius of Alexandria. The diocese no longer appears in Notitiae Episcopatuum from the end of the 15th century.
- Michel Lequien, Oriens christianus in quatuor Patriarchatus digestus, Paris 1740, Vol. I, coll. 401-404
- Raymond Janin, v. Cybistra ou Cybista, in Dictionnaire d'Histoire et de Géographie ecclésiastiques, vol. XIII, Paris 1956, coll. 1143-1144
- Annuario Pontificio 2013 (Libreria Editrice Vaticana 2013 ISBN 978-88-209-9070-1), p. 869
- This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed. (1911). "Heraclea". Encyclopædia Britannica. 13 (11th ed.). Cambridge University Press. p. 308.