Isaac Komnenos or Comnenus (Greek: Ἰσαάκιος Κομνηνός, Isaakios Komnēnos; c. 1155 – 1195/1196), ruled Cyprus from 1184 to 1191, before Richard the Lionheart, King of England conquered the island during the Third Crusade.
At the death of Byzantine emperor John II Komnenos in 1143, the throne passed not to his third and oldest living son, Isaac Komnenos (son of John II), but his youngest son, Manuel I Komnenos, who successfully claimed the throne. Isaac nevertheless served amiably as sebastokrator, and his first wife Theodora Kamaterina (d. 1144) bore him a daughter, Eirene Komnene, and other children. Eirene Komnene married an unnamed Doukas Kamateros and gave birth to Isaac Komnenos, a minor member of the Komnenos family, circa 1155.
One should not confuse Isaac with the Byzantine emperor Isaac I Komnenos (1057–1059), an uncle of Alexios I Komnenos and great-uncle of John II.
Byzantine historian Niketas Choniates provides most of the following account of his life. He was the son of an unnamed Doukas Kamateros who married Eirene Komnene, daughter of Isaac Komnenos.
Isaac Komnenos married an Armenian princess on Cyprus.
Emperor Manuel I Komnenos made Isaac governor of Isauria and the town of Tarsus (now in Mersin), where he started a war against the Armenian Kingdom of Cilicia, soldiers of which captured him. As Emperor Manuel died in 1180, seemingly nobody greatly cared about the fate of Isaac, whose long imprisonment seemingly failed to improve his general disposition. On account of his Armenian royal wife, he perhaps endured not too harsh terms of captivity.