Twin Falls, Waterfall in Olallie State Park, Washington, United States.

Twin Falls is a waterfall in Olallie State Park that descends in multiple stages along the South Fork Snoqualmie River. The water flows over different cascades before gathering in a natural basin.

The waterfall was modified for hydroelectric production, which affects water flow during dry months. These interventions help maintain natural currents in winter and spring.

The park was renamed Olallie in 1976 after the Chinook Jargon word for the berries common there; Twin Falls kept its English name. The surrounding Olallie State Park was created in 1950 from a 160-acre parcel bought from Puget Sound Power and Light.

The hiking trail is demanding and crosses a bridge with multiple viewing platforms along the river valley. Good footwear and attention to the path are necessary, especially in wet conditions.

Behind Twin Falls, a run-of-the-river hydroelectric project generates 24 MW of electricity, with its powerhouse buried 325 feet (99 m) below ground. Most visitors watching the 135-foot (41 m) drop never notice the underground plant.