The Nile, in northeast Africa, is generally listed as the longest river in the world at about 7,088 kilometers (4,404 miles). It flows north from its headwaters near Lake Victoria to the Mediterranean Sea, passing through Khartoum and Cairo before forming a large delta near Alexandria.
The Amazon carries far more water, and some measurements argue the Amazon is slightly longer, but the Nile remains the standard answer in most references. Its drainage basin spans eleven countries.
Source: Wikipedia, Nile