Which ancient city became Alexander's final capital?

The ancient city that became Alexander's final capital was Babylon. Alexander entered Babylon after defeating Darius III at Gaugamela in 331 BCE, and the city became the administrative center of his rapidly expanding empire.

Babylon was an especially powerful choice because it was one of the ancient Near East's greatest political and religious cities. It stood on the Euphrates in southern Mesopotamia and had served as a capital under the Neo-Babylonian and Achaemenid empires. Alexander respected its traditions, restored its temples, and used its established bureaucracy to govern the eastern territories he had conquered.

Alexander spent his final months in Babylon planning further campaigns, including a possible invasion of Arabia. He died there in June 323 BCE, making Babylon both the last capital of his reign and the setting of his death. Persepolis was an important Persian ceremonial capital, Alexandria was one of Alexander's major foundations, and Pella was his Macedonian homeland capital—not his final imperial seat.