The Nile is commonly recognized as the world's longest river, measuring about 6,650 kilometres.
It flows northward through northeastern Africa and empties into the Mediterranean Sea. The Nile's main tributaries include the White Nile and Blue Nile, which meet at Khartoum in Sudan. The Blue Nile rises at Lake Tana in Ethiopia, while the White Nile's headwaters extend into the Great Lakes region.
Ancient Egyptian civilization developed along the river's floodplain, where seasonal flooding deposited fertile sediment. The Aswan High Dam, completed in 1970, greatly changed the river's natural flood cycle.
Some studies argue that the Amazon may be longer depending on which source and mouth are selected. The Nile remains the standard answer in most reference works because river-length measurement methods differ.