The Stony River, also known as the Hangatahua River, is a significant waterway draining the northwestern slopes of Mount Taranaki in New Zealand's Taranaki region. It originates from the alpine Ahukawakawa Swamp at an elevation of approximately 2,100 meters and flows for 16 kilometers to its mouth at the Tasman Sea. The river's upper reaches lie within Egmont National Park, and it forms the boundary between the New Plymouth and South Taranaki districts. Historically regarded as Taranaki's premier trout fishery, the river's character has been shaped by its geology, with recent decades of erosion and land instability in its headwaters contributing to high sediment loads. The riverbed lives up to its name, featuring extensive cobble and gravel substrates that create ideal trout habitat with numerous riffles, runs, and pocket water.