Riverside is a borough in Northumberland County, Pennsylvania, United States.

Riverside lies on the south side of the North Branch of Susquehanna River, hence the name.

Riverside is connected to Danville by the Factory Street Bridge.

There were 799 housing units at an average density of 165.0 per square mile (63.7/km2).

23.2% of all households were made up of individuals, and 10.1% had someone living alone who was 65 years of age or older.