Leo IV, called Chozar or the Khazar (c. 750 – September 8, 780), succeeded his father, Constantine V, as emperor of the Byzantine Empire in 775. In 776 he associated his young son, Constantine, with himself in the empire, and suppressed an uprising led by his five step-brothers which broke out as a result of this proceeding.

Like his father and grandfather, Leo was successful in battle against the Arabs and Bulgars. Unlike his father and grandfather, however, Leo favoured the iconophiles, and restored an iconophile patriarch.

During his reign Leo was largely under the influence of his wife Irene, and when he died suddenly in 780 she was left as the guardian of his son and successor, Constantine VI.