Alexander V of Macedon (Greek: Ἀλέξανδρος Εʹ ὁ Μακεδών; died 294 BC) was the second son of Cassander and Thessalonica of Macedon, who was a half-sister of Alexander the Great. He ruled as King of Macedon along with his brother Antipater from 297 to 294 BC.
When Antipater murdered their mother and ousted him from power, Alexander turned to Pyrrhus and Demetrius I Poliorcetes for help in recovering his throne. To the former he promised, as the price of his alliance, the land on the sea-coast of Macedonia, together with the provinces of Ambracia, Acarnania, and Amphilochia. Demetrius, according to Plutarch, arrived after Pyrrhus had retired, and when matters had been settled between Alexander and Antipater. Demetrius was now an unwelcome visitor, and Alexander, while he received him with all outward civility, is said by Plutarch to have laid a plan for murdering him at a banquet, a plan which was stymied by the precautions of Demetrius. The next day Demetrius took his departure, and Alexander attended him as far as Thessaly. Here, at Larissa, Alexander went to dine with Demetrius, and, taking no guards with him, was assassinated, together with his friends who attended him.