Mazaeus was the Persian satrap who surrendered Babylon to Alexander the Great without a battle. He had commanded Persian forces at the Battle of Gaugamela in 331 BC, where Alexander defeated Darius III and shattered the empire’s main field army.
After the defeat, Mazaeus withdrew to Babylon. When Alexander approached, Mazaeus formally surrendered the city rather than attempting a hopeless defense. Babylon’s priests, officials, and inhabitants also came out to meet the conqueror, helping make the transfer peaceful. Alexander entered the city in October 331 BC.
Alexander rewarded Mazaeus with an unusually generous appointment: he allowed him to remain satrap of Babylon under Macedonian rule. A Macedonian officer supervised the garrison, while Mazaeus handled civil administration and continued issuing coinage. This arrangement helped Alexander present himself as a legitimate successor to the Persian king rather than merely a destroyer of Persian institutions.
A common mix-up is Bagophanes, who commanded Babylon’s citadel and participated in the formal surrender ceremony. Mazaeus, however, is the Persian governor most directly identified with surrendering Babylon itself.