Rio Oso is an unincorporated town in Sutter County, California, USA with a population of 963 residents. The ZIP Code is 95674. The community is inside area code 530.
In the state legislature Rio Oso is located in the 4th Senate District, represented by Republican Sam Aanestad, and in the 2nd Assembly District, represented by Republican Doug LaMalfa. Federally, Rio Oso is located in California's 2nd congressional district, which has a Cook PVI of R +13 and is represented by Republican Wally Herger.