Rio is a town in the suburbs of Patras and a former municipality in Achaea, West Greece, Greece. Since the 2011 local government reform it is part of the municipality Patras, of which it is a municipal unit. The municipal unit has an area of 98.983 km2. The municipal unit had a population of 14,219 in 2021. The campus of the University of Patras and the Casino Rio is located in Rio.

Achaea or Achaia, sometimes transliterated from Greek as Akhaia, is one of the regional units of Greece. It is part of the region of Western Greece and is situated in the northwestern part of the Peloponnese peninsula. The capital is Patras which is the third largest city in Greece.