|Administrative region:||West Greece|
|Population statistics (as of 2001)|
|- Area:||97.93 km2 (38 sq mi)|
|- Density:||136 /km2 (351 /sq mi)|
|Time zone:||EET/EEST (UTC+2/3)|
|Elevation (center):||40 m (131 ft)|
|Postal code:||265 xx|
Rio (Greek: Ρίο, Río, formerly Ῥίον, Rhíon; Latin: Rhium) is a town 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 former municipality had a population of around 13,000. The campus of the University of Patras is located in Rio.
Rio is the northernmost municipal unit of the Peloponnese peninsula. It stretches along the southeastern coast of the Gulf of Patras, about 7 km northeast of Patras city centre. The nearby Strait of Rio, crossed by the Rio–Antirrio bridge, separates the Gulf of Patras from the Gulf of Corinth to the east. The town is dominated by the Panachaiko mountain to the southeast.
The town centre is also known as Agios Georgios Riou. This is where the Rio railway station, on the line from Patras to Corinth, is located. The quarter Kastellokampos lies to the southwest of the centre. The ferry terminals, with services to Antirrio, are in the north, on both sides of the Rio–Antirrio bridge. There is a large fortress with bastions next to the bridge. The campus of the University of Patras and the hospital lie in the southeast, across the Greek National Road 8A. There are sandy beaches along the coast, and a port north of town centre.
The municipal unit Rio is subdivided into the following communities (constituent villages in brackets):
- Agios Vasileios
- Ano Kastritsi
- Arachovitika (Arachovitika, Kato Arachovitika)
- Kato Kastritsi (Kato Kastritsi, Magoula)
- Psathopyrgos (Psathopyrgos, Kato Rodini)
The name Rio derives from the Greek "ῥίον" (rhion), generally meaning "jutting part", perhaps from "ῥίς" (rhis), "nose", but also "spur of land". The earliest attested form of the word "ῥίον" (rhion) is the Mycenaean Greek ri-jo-no, from ri-jo, meaning "cape", written in Linear B syllabic script.
The site of Rio has been a strategic point since antiquity. Early 19th century, there stood an old Turkish castle (the Morea Castle) at the cape, with a small settlement outside its walls.
The mayors of the municipality were:
- Vasileios Zervas (1998–2006)
- Christos Liakopoulos (2006–2010)
- De Facto Population of Greece Population and Housing Census of March 18th, 2001 (PDF 793 KB). National Statistical Service of Greece. 2003.
- Kallikratis law Greece Ministry of Interior (Greek)
- ῥίον, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
- ῥίς, Henry George Liddell, Robert Scott, A Greek-English Lexicon, on Perseus Digital Library
- Palaeolexicon, Word study tool of ancient languages
- Leake, William Martin (1830). Travels in the Morea, Volume 2. London: John Murray. pp. 148–150.