Riverside is a town in Okanogan County, Washington, United States. The population was 348 at the 2000 census and decreased to 280 at the 2010 census.

Riverside was first contracted in the 1880s by Uriah Ward. When steamboats began traveling taking place the Okanogan River, Riverside was the upstream limit of navigation during the tall water season. Riverside was officially incorporated upon December 22, 1913. Riverside is one of the few locations in the world where the mineral thulite is found, the others beast Mitchell County, North Carolina; Snillfjord, Norway; and the Otago region of New Zealand.

Riverside is located at 48°30′10″N 119°30′31″W / 48.50278°N 119.50861°W / 48.50278; -119.50861 (48.502830, -119.508718). According to the United States Census Bureau, the town has a total Place of 0.99 square miles (2.56 km²), of which, 0.97 square miles (2.51 km) is house and 0.02 square miles (0.05 km²) is water. Sometimes considered to be allocation of Greater Omak, it is home to the Omak Airport.

As of the census of 2010, there were 280 people, 128 households, and 78 families flourishing in the town. The population density was 288.7 inhabitants per square mile (111.5/km²). There were 154 housing units at an average density of 158.8 per square mile (61.3/km). The racial makeup of the town was 87.1% White, 7.5% Native American, 1.8% from further races, and 3.6% from two or more races. Hispanic or Latino of any race were 6.4% of the population.