The Peneios (Πηνειος) was a River-God of Thessalia.
The Peneios was the main river of the Thessalian plain, flowing all the way from the Pindaros Mountains to enter the Aegean Sea by way of the Vale of Tempe. Peneios cutting a path between the Mount Olympos and Mt. Ossa. The most important neighbouring rivers were the Baphyras to the north, and the Anauros and Sperkheios to the south. Several of its tributories were also personified, such as the Enipeus, Titaressos, and Apidanos.
Peneios is best known for his involvement in the completion of Herakles' fifth labor. Herakles altered the usual flow of the rivers of both Peneios and Alpheios which washed away the waste.