Constantine, Constantinus, or Konstantinos (Κωνσταντῖνος) IV was a Byzantine and Eastern Roman emperor of the 7th century. He was the great-grandson of Heraclius. His reign was marked by successful defense against the Arabs who attempted to invade Constantinople with the first recorded use of Greek Fire according to the account of Saint Theophanes the Confessor. He oversaw the Third Council of Constantinople which condemned Monoenergism and Monothelitism.