Leonnatus ((356 BC – 322 BC) was a Macedonian officer of Alexander the Great and one of the diadochi.

He was one of Alexander's seven bodyguards, or somatophylakes. After Alexander died in 323 BC, the regent, Perdiccas, made Leonnatus satrap of Hellespontine Phrygia.

Leonnatus led an army of 20,000 infantry with 1,500 cavalry to relieve Antipater during the siege in Lamia (see Lamian War). He intervened probably with the ambition to usurp Antipater's power. A victory in battle against the Athenians would have certainly enhanced his claim to the throne. Leonnatus was killed in battle against the Athenians and his marriage with Cleopatra never took place.