Riolos (Greek: Ρίολος) is a village and a community in the municipal unit of Larissos, Achaea, Greece.

It is located on the northwestern edge of the Movri hills, 4 km north of Mataragka, 3 km southwest of Krinos, 6 km southeast of Lappas and 32 km southwest of Patras.

The community includes the small village Mazaiika.

The river Larissos flows southwest of the village.

During the Greek War of Independence a battle took place in Riolos in which the Greeks, led by Thallis Theodoridis the Elder, were victorious.