Demetrius I of Macedon was a king of Macedon who reigned from 239 to 229 BC. He was the son of Antigonus II Gonatas and belonged to the Antigonid dynasty. His rule was marked by efforts to strengthen the kingdom and maintain its independence amid external threats, particularly from the Aetolian League and Epirus. Demetrius I is known for his military campaigns and attempts to expand his territory. He faced challenges from rival factions and internal dissent, which ultimately led to his downfall. His reign ended when he was overthrown, and he was succeeded by Antigonus III Doson.