The Battle of Akroinon was fought on the western edge of the Anatolian plateau, in 740 between an Umayyad Arab army and the Byzantine forces. The Arabs had been conducting regular raids into Anatolia for the past century, and the 740 expedition was the largest in recent decades, consisting of three separate divisions. One division, 20,000 strong under Abdallah al-Battal and al-Malik ibn Shu'aib, was confronted at Akroinon by the Byzantines under the command of Emperor Leo III the Isaurian r. 717–741) and his son, the future Constantine V (r. 741–775). The battle resulted in a decisive Byzantine victory. Coupled with the Umayyad Caliphate's troubles on other fronts and the internal instability before and after the Abbasid Revolt, this put an end to major Arab incursions into Anatolia for three decades.

Akroinon was a major success for the Byzantines, as it was the first victory they had scored in a major pitched battle against the Arabs. Seeing it as evidence of God's renewed favour, the victory also served to strengthen Leo's belief in the policy of iconoclasm that he had adopted some years before. The Arab defeat at Akroinon has traditionally been seen as a decisive battle and a turning point of the Arab–Byzantine wars, causing the slackening of Arab pressure on Byzantium. Constantine V was able to take advantage of the Umayyad Caliphate's collapse to launch a series of expeditions into Syria and secure a Byzantine ascendancy on the eastern frontier which lasted until the 770s.