Danube is a city in Renville County, Minnesota, United States. The population was 505 at the 2010 census. Danube was laid out in 1899…Danube is a city in Renville County, Minnesota, United States. The population was 505 at the 2010 census. Danube was laid out in 1899, and named after the Danube, the European river. A post office called Danube has been in operation since 1903.