Riolos () 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.
Historic population
{| class="wikitable"
! Year !! Population
|-
| 1981 || 757
|-
| 1991 || 708
|-
| 2001 || 801
|-
| 2011 || 545
|-
| 2021 || 494
|}
See also
- List of settlements in Achaea