The Fall of Constantinople (Turkish: İstanbul'un Fethi; Greek: Άλωση της Κωνσταντινούπολης, Alōsē tēs Kōnstantinoupolēs) was the capture of Constantinople, the capital of the Byzantine Empire, which occurred after a siege by the Ottoman Empire, under the command of 21-year-old Ottoman Sultan Mehmed II, against the defending army commanded by Byzantine Emperor Constantine XI Palaiologos. The siege lasted from Friday, 6 April 1453 until Tuesday, 29 May 1453 (according to the Julian calendar), when the city was conquered by the Ottomans.
The capture of Constantinople (and two other Byzantine splinter territories soon thereafter) marked the end of the last remnant of the Roman Empire, an imperial state which had lasted for nearly 1,500 years. It was also a massive blow to Christendom, and the Ottomans thereafter were free to advance into Europe without an adversary to their rear. After the conquest, Mehmed made Constantinople the Ottoman Empire's new capital. Several Greek and non-Greek intellectuals fled the city before and after the siege, migrating particularly to Italy. It is argued that they helped fuel the Renaissance. Some mark the end of the Middle Ages by the fall of the city and empire.