The two longest rivers in the world are the Nile in Africa and the Amazon in South America. However, which is the longest is a matter of some debate. The Amazon has several mouths that widen toward the South Atlantic, so the exact point where the river ends is uncertain. If the Pará estuary (the most distant mouth) is counted, its length is approximately 4,195 miles (6,750 kilometers). The length of the Nile as surveyed before the loss of a few miles of meanders due to the formation of Lake Nasser behind the Aswan Dam was 4,145 miles (6,670 kilometers). The table below lists the five longest river systems in the world (exact figures vary, depending on sources).

^*Excluding Pará estuary