The Byzantine Iconoclasm were two periods in the history of the Byzantine Empire when the use of religious images or icons was opposed by religious and imperial authorities within the Ecumenical Patriarchate and the temporal imperial hierarchy. The First Iconoclasm, as it is sometimes called, occurred between about 726 and 787, while the Second Iconoclasm occurred between 814 and 842. According to the traditional view, Byzantine Iconoclasm was started by a ban on religious images promulgated by the Byzantine Emperor Leo III the Isaurian, and continued under his successors. It was accompanied by widespread destruction of religious images and persecution of supporters of the veneration of images. The Papacy remained firmly in support of the use of religious images throughout the period, and the whole episode widened the growing divergence between the Byzantine and Carolingian traditions in what was still a unified European Church, as well as facilitating the reduction or removal of Byzantine political control over parts of the Italian Peninsula.

The Byzantine Empire, also referred to as the Eastern Roman Empire, was the continuation of the Roman Empire centered in Constantinople during Late Antiquity and the Middle Ages. The eastern half of the Empire survived the conditions that caused the fall of the West in the 5th century AD, and continued to exist until the fall of Constantinople to the Ottoman Empire in 1453. During most of its existence, the empire remained the most powerful economic, cultural, and military force in the Mediterranean world. The term "Byzantine Empire" was only coined following the empire's demise; its citizens referred to the polity as the "Roman Empire" and to themselves as "Romans". Due to the imperial seat's move from Rome to Byzantium, the adoption of state Christianity, and the predominance of Greek instead of Latin, modern historians continue to make a distinction between the earlier Roman Empire and the later Byzantine Empire.