The South Nahanni River is a major tributary of the Liard River, located roughly 500 kilometres west of Yellowknife in the Northwest Territories of Canada. It is the centerpiece of Nahanni National Park Reserve. It flows from the Mackenzie Mountains in the west, through the Selwyn Mountains, growing as it heads east over the majestic Virginia Falls, and finally empties into the Liard River. The Nahanni has a unique geological history. It was formed when the area was a broad flat plain, forming a winding course typical of flatland rivers.