When asked, "What is the longest river in the world?" One cannot give you the exact answer because there is no perfect measure of the length of a river. Rivers are not constant and there have always been disputes about where the sources of certain rivers are. In fact there are still arguments about whether or not the Nile is actually the longest river in the world as opposed to the Amazon. Because of this, compiling a list of which rivers are recognized as the longest in the world is difficult. Below is a list of what are generally considered the ten longest rivers in the world.

The Nile has long been considered the longest river in the world. It is about 4,135 miles (6,650 km) in length and flows in a northward direction to where it finally drains into the Mediterranean Sea. It passes through ten countries on the continent of Africa, where it has been a main source of water and life since ancient times. The Nile has two main contributories, the White Nile and the Blue Nile. The White Nile is the longer of the two, but the Blue Nile feeds the river more water.

The Amazon is approximately 3,980 miles (6,400km) in length and is known as the second longest river in the world. It passes through seven countries in South America and is actually the largest river in terms of volume and flow. In fact, it accounts for one-fifth of the world's river flow. For these reasons scientists dispute that it should be considered the longest river in the world as well, but this title is not yet theirs.

The Yangtze River (also called the Chang Jiang) is about 3,915 miles (6,380 km) in length and is considered the third longest river in the world. It is located in the People's Republic of China and it flows from its source in the Qinghai Province, to the East China Sea at Shanghai. Because it is the largest river in this region it is important economically, historically and culturally. It also id the home of the world's largest hydro-electric power system, the Three Gorges Dam.

The Missouri-Mississippi River system at about 3,900 miles (6,300 km) in length, it is the fourth longest river in the world. Its average discharge of water makes it the tenth largest river in the world. It is the only river located in North America that made the top ten longest rivers list. Also, its name comes from an Ojibwe word meaning "Great River". About 98.5 percent of this river is located within the United States, the rest resides in Canada.

The Yenisei is thought of as the greatest river system that flows in the Arctic Ocean and at 3,445 miles (5,539 km), is the fifth longest river in the world. It is in Russia and is mainly in the Siberian region. This river includes several hydro-electric dams that fuel a significant part of Russia's primary industry.

The Yellow River (also called the Huang He) is the second longest river in the People's Republic of China and is the sixth longest in the world being about 3,010 miles (4,845 km) in length. In china it is known by both positive and negative nicknames. The positive one being "the cradle of China" because it is the birthplace of northern Chinese civilization and the negative one being "China's sorrow" because of the flooding that occurs that causes a large amount of damage.

The Ob-Irtysh river system makes up the seventh largest river in the world. The Irtysh is a tributary of the Ob and is actually longer than the Ob. These rivers are located in Siberia and together are about 3,364 miles (5,410 km) in length. They form a major basin in Asia, encompassing most of Western Siberia and the Altay Mountains.

The Congo River (also called the Zaire River) is the second largest river in Africa and the eight largest in the world. It is about 2,922 miles (4,700 km) long. It has both the second largest flow and the second larges draining basin in the world, only following the Amazon. The Congo has its name because of the Kingdom of Kongo that inhabited the area at the mouth of the river in ancient times. It is known as the Zaire River only because between 1971 and 1997he area was known as Zaire and the government called it the Zaire River until the country be came the Republic of Congo.

The Amur River (also called the Heilong Jiang) is the world's ninth longest river and is also the border between the Russian Far East and Northeastern China. This River flows across northeast Asia to the Strait of Tartary, where it finally drains into the Pacific Ocean. It was has been called the" Black River" because it was sacred to the Manchu and the Qing Dynasty and it is also a symbol of Russian-Chinese relations.

The Lena River is Russia's greatest river and being approximately 2,800 miles (4,400 km), it also the world's tenth longest river. This river has seven different tributary rivers that join with it and they are the Kirenga River, the Olyokyma River, the Vitim River, the Amga River, the Aldan River, the Vilyuy River and the Maya River. It has the unique distinction of the River who appears to be the largest river in the world when looked at with a Mercator projection.