The siege of Negroponte was fought between the forces of the Ottoman Empire, led by Sultan Mehmed II in person, and the garrison of the Venetian colony of Negroponte (Chalcis), the capital of the Venetian possession of Euboea in Central Greece. The Ottoman sultan Mehmed II laid siege to the fortress at Negroponte. It lasted for almost a month, and despite great Ottoman casualties ended in the capture of the city and the island of Euboea by the Ottomans.

Mehmed II, commonly known as Mehmed the Conqueror, was twice the sultan of the Ottoman Empire from August 1444 to September 1446 and then later from February 1451 to May 1481.