Alexander V of Macedon is the third and youngest son of Cassander and Thessalonica of Macedon, who is a half-sister of Alexander the Great.

He rules as King of Macedon along with his brother Antipater from 297 to 294 BCE.

When Antipater murders their mother and ousts him from power, he turns to Pyrrhus and Demetrius I Poliorcetes for help in recovering his throne.

To the former he promises, 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, he went to dine with Demetrius, and, taking no guards with him, was assassinated, together with his friends who attended him.