Alcetas (Greek Ἀλκέτας; died 320 BC) was the brother of Perdiccas and the son of Orontes from Orestis.
At Perdiccas' orders, in 323 BC Alcetas murdered Cynane, the half-sister of Alexander the Great, as she wished to marry off her daughter Eurydice to Philip Arrhidaeus, the nominal king of Macedon.
[2] At the time of Perdiccas' murder by his own troops in Egypt in 321 BC, Alcetas was with Eumenes in Asia Minor engaged against Craterus.
The war against Alcetas, who had now left Eumenes and united his forces with those of Attalus, was waged by Alexander's general Antigonus.
The youth, greatly resenting what had happened, recovered Alcetas' corpse, buried it with full honours, and erected a beautiful monument to his memory.