Lake Cascade, Artificial reservoir in Valley County, Idaho, US.

Lake Cascade is a 47-square-mile reservoir on the North Fork of the Payette River in Valley County, Idaho, held back by an earthen dam completed in 1948. It lies in the Boise National Forest at 1,473 metres, stretching about 21 km north to south and 8 km east to west. Its shoreline includes a small cove near a curving grey road on the eastern edge.

The earthen dam on the North Fork of the Payette River was built by the Bureau of Reclamation and completed in 1948, after a delay caused by World War II. The reservoir was long called Cascade Reservoir; "Lake Cascade" came into common use in the 1990s and became the federal name in 1999.

The name Cascade Reservoir gave way to Lake Cascade in common use during the 1990s, and the federal name change followed in 1999. Around the water, Lake Cascade State Park manages several separate units, and Tamarack Resort occupies the west shore southwest of Donnelly. Ice fishing draws anglers onto the frozen surface in winter.

The reservoir offers boating, fishing, and camping opportunities during warmer months and ice fishing in winter. Multiple shoreline areas provide accessible entry points for various activities throughout the year.

In 2003 the Idaho Department of Fish and Game proposed draining the reservoir to remove pikeminnow, predators that live up to 15 years and compete with sport fish. The Bureau of Reclamation withdrew the request for an environmental study, calling the draining not viable.