According to U.S. Geological Survey, the River Nile is the world longest river with length of  4,132 miles (6,650 kilometers).

Next in the line Longest Rivers in the World are:

Amazon River - 4,000 miles (6,437 kilometers)

Yangtze River  - 3,915 miles (6,301 kilometers)

The longest U.S. river is the Missouri with 2,540 miles (4,088 kilometers)


Where is the River Nile?

The River Nile is the longest river in the world. The flow of the Nile is 4,132 miles (6,650 kilometers).
The Nile River flows from south to north through the northeastern part of Africa, mainly through Sudan and Egypt.
Annual flooding of the Nile have made the Nile valley, which is located in the hot, dry and barren desert, fertile strip of land inhabited by people for thousands of years.

Nile arises from two major rivers - the White and Blue Nile.

White Nile flows out of Lake Victoria, which is located in Uganda. White Nile has more or less the same  water level trough the year and it can’t be the cause of the annual increase in water in the river Nile. In April and May, when the water level is the lowest of the Nile, 85 percent of the Nile water is water  from the White Nile.
However, the Blue Nile source is in Ethiopia.
The Ethiopian mountains have a lot of rains and a lot of snow is melting there. All this water coming from the Blue Nile, increases the water level in the River Nile.