Determining the world's longest river is more challenging than you might think. There's often debate over where a river actually starts. With that in mind, we looked into the most agreed-upon top six longest rivers in the world. Here they are.

Yellow River

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The Yellow River, also known as the Huang He, is the sixth longest river in the world and the second longest in China. The river measures 3,395 miles long, and runs from the Bayan Har Mountains in Western China to the Bohai Sea. While the Yellow River was the birthplace of ancient Chinese culture, it has also caused deadly floods and is responsible for several natural disasters.

Yenisei River

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The Yenisei River in Siberia measures 3,445 miles long. Starting in Lake Baikal, the river eventually makes its way to the Arctic Ocean. The Yenisei is one of the three great Siberian rivers, which also includes the Ob and the Lena.  

Mississippi River

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The fourth largest river in the world, the 3,902-mile-long Mississippi River runs from northern Minnesota to the Gulf of Mexico. The area where the river meets the sea is known as the Mississippi River Delta. More than just a straight shot dividing the country, the Mississippi is part of the largest river system in North America.

Yangtze River

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Not only is the Yangtze river the third longest river in the world, but it is also the longest river in Asia at 3,917 miles. It also happens to be the longest to flow through one country, as the entire river is located within China. As much as one third of the Chinese population resides within the Yangtze River basin.

Amazon River

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Though a collection of scientists believe the Amazon to be the longest river in the world, confusion over where the river actually begins places it second on this list.

The currently agreed upon length is around 3,976 miles, though, like we mentioned, some say the river is longer. If currently argued values are proven and accepted, the river could be as long as 4,435 miles.

Nile River

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Though it may one day be displaced from its throne by the Amazon, the Nile is currently considered to the longest river in the world, with a generally agreed upon length of around 4,132 miles. This figure could be even longer, actually, with some saying the true length of the river is 4,405 miles.

The Nile is widely known for providing water to Egypt, but is also shared by Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia and Uganda.