The Manu is a river in southeastern Peru. It runs down the eastern slopes of the Andes Mountains into the Amazon Basin. It runs through what is now protected as the Manu National Park, a vast Biosphere Reserve, home to arguably the highest concentration of biodiversity on Earth. Few people live along its length. Much of the park is off-limits to all but permitted scientists and the indigenous groups of Amazonian Indians, mostly of the Machiguenga tribe.