Athenaeus the Mechanicus was a Hellenistic military engineer of the 1st century BCE. Little is known of his biography, but his surviving treatise indicates he was a professional active during a period of significant development in siege warfare. This dating is based on internal evidence and his apparent influence on later writers such as Vitruvius.

His sole extant work is the treatise On Machines, dedicated to a Marcellus, who is often tentatively identified as the Roman general Marcus Claudius Marcellus. The text provides practical instructions on the construction and use of siege engines.

Athenaeus is a significant figure as one of the few surviving technical writers on Hellenistic military engineering. His work is a valuable source for the history of ancient siegecraft and represents an important link in the transmission of Greek mechanical knowledge to the Roman world, with clear parallels to the later work of Vitruvius.