Theophanes (died 817 or 818) was a Byzantine monk and chronicler.

He was born in the 750s of iconodule aristocratic parents, but was orphaned at an early age, and the emperor Constantine V saw to his education and upbringing. His chronicle preserves a vibrant childhood memory of icebergs created from the thawing of the frozen Black Sea, and floating past Constantinople in February of 764. Under Leo V he received the title of spatharios. He later founded a monastery near Sigiane on the Asian side of the Sea of Marmora, where he lived until his death.

His chronicle of world events from 284 (the point where the chronicle of George Syncellus ends) to 813, is valuable for preserving the materials of Byzantine history that would be otherwise lost for the seventh and eighth centuries. This chronicle was translated into Latin by the papal librarian Anastasius in the second half of the ninth century, and thus was known to Western Europe.