Riverside is a town in Okanogan County, Washington, United States.

When steamboats began traveling up the Okanogan River, Riverside was the upstream limit of navigation during the high water season.

Riverside is one of the few locations in the world where the mineral thulite is found, the others being Mitchell County, North Carolina; Orkland, Norway; and the Otago region of New Zealand.

There were 154 housing units at an average density of 158.8 per square mile (61.3/km2).

32.8% of all households were made up of individuals, and 10.9% had someone living alone who was 65 years of age or older.

There were 153 housing units at an average density of 171.2 per square mile (66.4/km2).

24.5% of all households were made up of individuals, and 11.9% had someone living alone who was 65 years of age or older.