Rio Dell (formerly, Rio Del and Eagle Prairie) is a city in Humboldt County, California, United States. Rio Dell is located on the west bank of the Eel River 1 mile (2 km) north of Scotia, at an elevation of 161 feet (49 m). The population was 3,363 at the 2010 census, up from 3,174 at the 2000 census.
Rio Dell was first named Eagle Prairie, but was renamed to Rio Dell in 1890. The name River Dell was first suggested, but as the name was too similar to Riverdale, CA, the name of town became Rio Dell.