The Ottoman conquest of the Morea occurred in two phases, in 1458 and 1460, and marked the end of the Despotate of the Morea, one of the last remnants of the Byzantine Empire, which had been extinguished in the Fall of Constantinople in 1453.
The Despotate of the Morea had been founded as an autonomous appanage ruled by members of the Byzantine imperial Palaiologos dynasty. During the 14th and 15th centuries, it was the scene of the last flourishing of Byzantine culture, but in the 1420s it was repeatedly attacked by Ottoman raiders under Turahan Bey, and was reduced to a tributary vassal by Sultan Murad II in 1446. From 1449, it was ruled by the brothers Demetrios Palaiologos and Thomas Palaiologos, who were engaged in a constant rivalry with one another: they divided the Morea peninsula among themselves, and neglected the payment of tribute to the Sultan. Having lost his patience with the quarreling brothers, and determined to avoid the Morea being used as a springboard for a Western crusade against him following his capture of Constantinople, Sultan Mehmed II invaded the peninsula in May 1458. While part of his forces besieged the Acrocorinth, the rest ravaged the peninsula. After the fall of the Acrocorinth, the two Palaiologoi brothers capitulated. Acrocorinth, Thomas' capital, Patras, and much of the northern part of the peninsula came under direct Ottoman rule; the Palaiologoi were left as tributary rulers in the southern half, which included the Despotate's capital, Mystras.
As soon as the Sultan left, the quarrel between the two brothers resumed, with Demetrios moving to a pro-Ottoman stance and Thomas, who had lost most of his domain, increasingly looking for Western assistance. Thomas rose in revolt in January 1459, leading Demetrios to call for Ottoman assistance from the governors installed in the northern peninsula. Mehmed II tried to mediate between the brothers, but the civil war resumed soon after. Bolstered by Italian reinforcements, Thomas gained the upper hand; Demetrios withdrew to Monemvasia and sent envoys to beg the Sultan for his assistance, while Pope Pius II tried to rally Western support for an anti-Ottoman crusade at the Council of Mantua. In April 1460, Mehmed II led his second invasion of the Morea. He first secured the surrender of Demetrios and the remaining territories under the latter's control, including Mystras, before moving west to the lands held by Thomas, who fled to Corfu with his family. The last sources of resistance in the peninsula were subdued in July 1461, and the Morea became an Ottoman province. Ottoman rule would be challenged during the First Ottoman–Venetian War, which broke out in 1463, and in which the Republic of Venice would unsuccessfully attempt to capture the peninsula; and the remaining Venetian coastal strongholds would be gradually reduced by 1540. Apart from a period of Venetian rule in 1685–1715, the Morea would remain in Ottoman hands until the outbreak of the Greek War of Independence in 1821.