The longest river in Egypt is the Nile.

An excerpt from the article 15 facts about Egypt

It was the Nile that allowed the first civilizations to settle in this area. Annual floods of the river fertilized the coastal areas, fertilizing them and increasing the possibilities of growing cereals.

The river is 6650 km long and is the longest in Africa and the second longest in the world. Until recently, it was believed to be the longest river in the world, but an expedition by the Brazilian Institute of Geography and Statistics showed that the Amazon is 105 kilometers longer than it.