The Waimea River is the largest and the longest river on the island of Kauai in the U.S. state of Hawaii.

At 35.7 km (22.2 mi) in length,[1] it is the 3rd longest river in the Hawaiian Islands, draining one sixth of the total area of the island.

It rises in a wet plateau of the island's central highlands, in the Alaka'i Swamp, the largest high-elevation swamp in the world.

It enters the Pacific Ocean at Waimea, near the 1778 landing place of Captain Cook on Kauai.

This article related to a river in Hawaii is a stub.