Alcetas II (Greek: Ἀλκέτας B' ὁ Μακεδών; died 448 BC) was king of the ancient Greek kingdom of Macedon.
Alcetas was the eldest son of Alexander I and an unknown queen; he was a grandson of Amyntas I and Eurydice. He became king of Macedon following the death of his father in 454 BC. His brothers were Perdiccas II and Prince Philip(pus). He was known for his alcohol dependence. After 6 years as king, he was killed by his nephew Archelaus. Alcetas's younger brother (Archelaus' father) Perdiccas then took over the Macedonian throne.