Constantine IV (Greek: Kōnstantinos IV, Latin: Constantinus IV), (c. 652 – September 685), sometimes incorrectly called Pogonatos, "the Bearded", by confusion with his father; is Byzantine Emperor from 668 to 685.

His reign sees the first serious check to nearly 50 years of uninterrupted Islamic expansion, while his calling of the Sixth Ecumenical Council sees the end of the monothelitism controversy in the Byzantine Empire.