Who was the Persian King that faced Alexander the Great at the Battle of Guagamela?

The Persian King who faced Alexander the Great at the Battle of Gaugamela was Darius III. This battle, fought in 331 BC, was a significant confrontation during Alexander's campaign to conquer the Persian Empire. Darius III led a vast army in an attempt to stop Alexander's advance, but despite his numerical advantage, he was ultimately defeated, which marked a crucial turning point in Alexander's conquests.

Darius III was a member of the Achaemenid dynasty and had lost control over much of his empire due to various factors, including internal strife and the pressure from Alexander's military tactics. Understanding his role in this battle helps illustrate the broader context of the conflict between Greece and Persia, particularly during the period of Hellenistic expansion initiated by Alexander.

Cyrus the Great, Xerxes, and Artaxerxes were notable Persian kings, but they ruled before Darius III. Cyrus the Great founded the Achaemenid Empire, Xerxes I is famous for his conflicts with the Greeks during the Persian Wars, and Artaxerxes is known for his reign during a later period that did not coincide with Alexander's conquests. Therefore, Darius III is the correct answer in the context of the Battle of Gaugamela