Alexarchus of Macedon was a historian active in the late 4th and early 3rd centuries BCE. He was the brother of King Cassander of Macedon and a son of the regent Antipater, placing him within the Macedonian elite during the Wars of the Diadochi. No further biographical details survive.

He authored a now-lost history of India titled Indica. This work survives only in a single citation by the Roman author Aulus Gellius, who references Alexarchus for a story about a talking snake.

Alexarchus’s significance stems from his aristocratic lineage and his contribution to the Hellenistic genre of Indica. His work represents the literary interest in India following Alexander the Great's expedition, alongside authors like Megasthenes. The surviving fragment suggests his history included ethnographic marvels typical of the period.