Honopū Valley is a landmark valley within Nā Pali Coast State Park along the northwest shore of Kauaʻi, Hawaiʻi, United States. It is known for its distinctive natural arch, which at approximately 90 feet (27 m) tall is the tallest in Hawaii. At the lower end of the valley is Honopū's secluded, 0.25-mile (0.40 km) beach, also known as Cathedral Beach.