Which city was formerly known as Constantinople?

The city formerly known as Constantinople is Istanbul.

The city stands on the Bosporus, linking Europe and Asia, and has carried several important names. It began as Byzantium, an ancient Greek settlement. In the fourth century, Roman emperor Constantine the Great selected it as a new imperial capital and associated it with the name Constantinople, meaning the city of Constantine.

Constantinople became the capital of the Byzantine, or Eastern Roman, Empire and remained one of the world's most important political, commercial, and religious centers. Ottoman forces led by Mehmed II captured the city in 1453, after which it became the Ottoman capital. The Ottoman Empire later moved its capital to Ankara after the Turkish Republic was established.

Istanbul was already used in everyday speech during the Ottoman period, probably deriving from a Greek phrase meaning “to the city.” Turkey officially standardized the city's name as Istanbul on March 28, 1930. Constantinople still appears in historical and religious contexts, including the title of the Ecumenical Patriarch, but Istanbul is the modern city's official name.