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Ría is a coastal geomorphological term used in Iberian and Atlantic European contexts to describe a type of estuary: a drowned river valley that forms a long, narrow inlet along the coast. Unlike fjords, which are formed by glacial processes, rías result when rising sea levels flood low-lying river valleys, leaving multiple subinlets connected to the sea. They typically feature deep, steep sides, branched arms, and broad tidal flats, with brackish water in inner sections and saltwater near the mouth. The coastline is often irregular, with islands and peninsulas.

Rías are common on the Atlantic coasts of Galicia (Spain) and Portugal, where the term is widely used in place names and regional geography. In Galicia, notable rías include the Ría de Arousa, the Ría de Pontevedra, and the Ría de Vigo, as well as the Ría de Muros e Noia. In Portugal, notable examples include the Ria Formosa along the Algarve and the Ria de Aveiro near Porto. The concept is also recognized in other Atlantic regions of Europe, including Brittany and Cornwall, where similar inlets occur.

Economically, rías host important fisheries and shellfisheries, notably mussel and oyster farming, and they are popular for tourism and maritime activities. Ecologically, they support diverse communities of birds, fish, and invertebrates but are sensitive to pollution and coastal development, making many rías designated as protected or monitored areas.

The term ría derives from Galician-Portuguese and is a standard term in physical geography for such inlets. In English-language geography, ría is often translated as ria or estuary, depending on the context.