Aelian the Tactician was a Greek military writer active during the reigns of the Roman emperors Trajan and Hadrian in the early 2nd century CE. He is distinguished from the later Claudius Aelianus, known as Aelian the Sophist, and was a contemporary of the historian Arrian. He dedicated his work to Hadrian, indicating his status as a Greek intellectual operating under Roman imperial patronage.

His sole known work is the Tactica Theoria, also known as On Tactical Arrays of the Greeks, a systematic treatise on Greek and Macedonian military tactics. Aelian’s significance stems from his compilation of Hellenistic military doctrine, particularly the Macedonian phalanx system. His theoretical study became a foundational text for later military thought. It was used by Vegetius in the 4th century, informed the Byzantine emperor Leo VI’s Tactica, and influenced Renaissance military theory, making it a crucial link in the transmission of ancient military science.