Ioannes IV (, Iōannēs D΄) may refer to: Patriarch John IV of Constantinople (died in 595) John IV, Archbishop of Ohrid (c. 1088 – 1163/64) John IV Laskaris (1250–c. 1305) John IV Megas Komnenos (c. 1403–1459), emperor of Trebizond See also John IV (disambiguation)