Polyaenus or Polyenus was a 2nd-century CE Greek author, known best for his Stratagems in War, which has been preserved. He was born in Bithynia. The Suda calls him a rhetorician, and Polyaenus himself writes that he was accustomed to plead causes before the Roman emperor. Polyaenus dedicated Stratagems in War to the two emperors Marcus Aurelius and Lucius Verus, while they were engaged in the Roman–Parthian War of 161–166, about 163, at which time he was too old to accompany them in their campaigns.