Nonnosus (Greek: Νόννοσος, translit. Nónnosos) was a Byzantine ambassador under Justinian I. He led a mission to the Red Sea area, visiting Axum, Ḥimyar, and the Arabs.
Upon his return he wrote a history of his embassy, which has survived only in a condensed version form attributed to Photios I of Constantinople. This claims that his father, Abraham, had been an ambassador to the Arabs and that his uncle, also Nonnosus, was sent on an embassy by Anastasius I.