Polyaenus or Polyenus (/ˌpɒliˈiːnəs/ POL-ee-EE-nəs; see ae (æ) vs. e; Greek: Πoλύαινoς, Polyainos, "much-praised") was a 2nd-century Macedonian author, known best for his Stratagems in War (in Greek, Στρατηγήματα), which has been preserved. The Suda calls him a rhetorician, and Polyaenus himself writes that he was accustomed to plead causes before the emperor. He dedicated Stratagems in War to Marcus Aurelius (161–180) and Verus (161–169), while they were engaged in the Parthian war (162–165), about 163 CE, at which time he was too old to accompany them in their campaigns.
This work is divided into eight books, of which the first six contain an account of the stratagems of the most celebrated Greek generals, the seventh of those of foreign people, and the eighth of the Romans, and illustrious women. Parts, however, of the sixth and seventh books are lost, so that of the 900 stratagems which Polyaenus described, 833 have survived.
The book has survived through a single copy of the 13th century, which once belonged to Michel Apostolios and is now in the Laurentian Library in Florence. The work is written in a clear and pleasing style, though somewhat tinged with the artificial rhetoric of the age. It contains a vast number of anecdotes respecting many of the most celebrated men in antiquity, and has uniquely preserved many historical facts.