Nikephoros I of Constantinople was a Byzantine prelate, historian, and writer who served as the Ecumenical Patriarch from 806 to 815. Born into an Orthodox family in Constantinople, he initially served the empire as an imperial secretary before retreating to the monastic life. His tenure as patriarch was marked by significant theological conflict regarding iconoclasm, leading to his eventual removal from office. He remained a dedicated defender of the veneration of icons, continuing his polemical writings even after being forced into monastic seclusion.