The Earth's longest river is the Nile in Africa. The Nile was very important to the people of ancient Egypt; the annual flooding of the Nile helped to keep Egyptian soil fertile.

Ancient Egyptians developed a system of astronomy in order to predict when the Nile was flood.

The Nile is at 6,695 kilometers (4,160 miles) long. It flows northward from Lake Victoria, which lies between Tanzania, Kenya and Uganda, passes through Uganda, South Sudan, Sudan and Egypt, then finally empties into the Mediterranean Sea.  Several different rivers flow into Lake Victoria, so it cannot be considered the true source of the Nile.

Tributaries of the Nile flow through Tanzania,  Burundi, Rwanda, the Democratic Republic of the Congo, Kenya and Ethiopia.

In ancient times, the Nile also served as an important trade route.

After the Nile, the longest rivers on Earth are:

2nd - Amazon, in South America: 6,516 kilometers (4,049 miles) long.  The Amazon River discharges more water than any other river on Earth and has the Earth's largest drainage basin. Most of the drainage basin is covered by the Amazon rainforest.

3rd - Yangtze, in Asia: 6,380 kilometers (3,965 miles) long. The Yangtze River runs through China. It was once the home of a rare dolphin known as the Yangtze River Dolphin, which is now believed to be extinct.

4th - Mississippi-Missouri, in North America: 5,969 kilometers (3,709 miles) long. The Mississippi-Missouri river basin was formed by glacial action during the last Ice Age. The Mississippi-Missouri River is the setting for many works by the American writer, Mark Twain.

Ob River5th - Ob-Irtysh, in Asia: 5,568 kilometers (3,460 miles) long.  The Ob-Irtysh River runs through Siberia and empties into the Arctic Ocean. It has tributaries in China, Mongolia and Kazakhstan. The Ob-Irtysh River is frozen for a large part of the year.

6th - Yenisey-Angara-Selenga, in Asia: 5,550 kilometers (3,449 miles) long.  The Yenisey-Angara-Selenga River runs through Mongolia and Siberia and, like the Ob-Irtysh, empties into the Arctic Ocean and is frozen for much of the year.

7th - Yellow, in Asia: 5,464 kilometers (3,395 miles) long.  The Yellow River runs through China. Chinese civilization began on the Yellow River basin.

8th - Congo, in Africa: 4,667 kilometers (2,900 miles) long.  The Congo is believed to be the deepest river in the world.

9th - Río de la Plata-Paraná, in South America: 4,500 kilometers (2,796 miles) long. Buenos Aires, in Argentina and Montevideo, in Uruguay are located on the shores of the - Río de la Plata-Paraná.  This river is home to the La Plata dolphin.

10th - Amur-Argun, in Asia:  4,444 kilometers (2,763 miles)long. The Amur-Argun river forms part of the border between China and Russia, and islands in the river have been the source of territorial disputes between the two countries.

The longest river in Europe is the Volga, which is 3,688 kilometers (2,292 miles) long.  It is located in Russia, and flows into the Caspian Sea. The Volga basin  is known as the birthplace of Russian culture.

The Murray-Darling, in southeastern Australia,  is the longest river in Australia. It is 3,672 kilometers (2,282 miles) long. The Murray-Darling River basin is home to many endangered animal species.