Onasander or Onosander (Greek: Ὀνήσανδρος Onesandros or Ὀνόσανδρος Onosandros; fl. 1st century AD) was a Greek philosopher. He was the author of a commentary on the Republic of Plato, which is lost, but we still possess his Strategikos (Στρατηγικός), a short but comprehensive work on the duties of a general. It is dedicated to Quintus Veranius Nepos, consul in AD 49, and legate of Britain. It was the chief authority for the military writings of the emperors Maurice and Leo VI, and Maurice of Saxony, who consulted it in a French translation and expressed a high opinion of it.
Onasander's Strategikos is one of the most important treatises on ancient military matters and provides information not commonly available in other ancient works on Greek military tactics, especially concerning the use of the light infantry in battle.
- Aeneas Tacticus, Asclepiodotus, and Onasander. Translated by Illinois Greek Club. Loeb Classical Library. ISBN 0-674-99172-9
- Kai Brodersen: Onasandros: Gute Führung / Strategikos. (Greek and German.) Marix, Wiesbaden 2018, ISBN 978-3-7374-1074-8.
- Onasander (complete text of the English translation, from the Loeb edition)