Waimea Canyon State Park, State park and canyon in Kauai County, United States.

Waimea Canyon State Park is a nature reserve featuring a wide canyon that stretches for ten miles across western Kauai. The walls display red and brown volcanic rock formations, with depths reaching up to 3,000 feet.

Kauaʻi's oldest lavas date to about five million years ago. Around four million years ago, part of the island collapsed along a large fault, forming a depression that later filled with thick lava flows. Rainwater from Mount Waiʻaleʻale then cut Waimea Canyon along the edge of that collapse.

Waimea is Hawaiian for "reddish water", named for the red soil washed down by the Waimea River. The river is fed by rain on Mount Waiʻaleʻale, among the wettest places on earth. The rare tree Hibiscadelphus distans is endemic to the canyon.

Visitors can access multiple viewpoints along Highway 550, with some requiring parking fees. Arriving early is recommended, and wearing comfortable hiking shoes helps when exploring the various trails throughout the area.

The rock walls contain layers of black basalt that have transformed into bright red colors through continuous exposure to natural elements. This color change is a visible sign of the location's ancient geological history.