The penestae (in Greek oι Πενέσται, hoi penestai) were a class of unfree labourers tied to the land once inhabiting Thessaly, whose status was comparable to that of the Spartan helots.
Tradition made the penestae descendants of the Achaeans subjected by invading tribes arriving from Thesprotia. Archemachus (cited by Athenaeus, VI, 264), a 3rd century BC writer, believed instead that they were Boeotians:
"The Aeolian Boeotians who did not emigrate when their country Thessaly was conquered by the Thessalians, surrendered themselves to the victors on condition that they should not be carried out of the country, nor be put to death, but should cultivate the land for the new owners of the soil, paying by way of rent a portion of the produce of it, and many of them are richer than their masters."
The Thessalian lands were very productive and spacious (in comparison to the size of the population, i.e.); the penestae thus had goodly amounts of rich land to cultivate. The contributions given to the Thessalians (and Archemachus' remark about their wealth) imply that the penestae could freely dispose of the portions in excess of their rent payments, and that they could possess goods. Certain penestae, known as latreis, worked as house servants, receiving in exchange a salary.
Dionysius of Halicarnassus tells us (II, 9) that they were beaten when they refused to obey and that, generally speaking, they were treated like chattel slaves (i.e. people considered to be the property of others). They appear to have been much less numerous than the free Thessalians.
From a passage in Demosthenes it appears that the penestae sometimes accompanied their masters to battle, and fought on horse-back as their knights or vassals. This circumstance is not surprising, in view of the fame of the Thessalian cavalry. The penestae of Thessaly also resembled the Laconian helots in another respect, for they often rose up in arms against their lords. There were penestae among the Macedonians also. There were also an Illyrian tribe called Penestae.