Which is the longest river in the world?

The Nile and the Amazon are the two longest rivers and their order is debated. The Nile is traditionally cited at about 6,650 km, while some surveys give the Amazon a slightly greater length depending on which headstream and mouth are measured.

Why do river lengths vary between sources?

River length depends on where you start measuring the source and where you call the mouth, both of which are ambiguous for braided deltas and seasonal headstreams. Different surveys make different choices, so figures vary by tens or hundreds of kilometres.

What is the difference between length and discharge?

Length is how far the river runs; discharge is how much water it carries. The Amazon is by far the largest by discharge, carrying roughly a fifth of the world's river flow, even though its length is close to the Nile's.

What does the outflow column show?

The outflow is the sea, ocean, or basin the river ultimately drains into, such as the Mediterranean for the Nile or the Atlantic for the Amazon. It tells you which drainage basin and ocean the river belongs to.

Are these main rivers or whole river systems?

The lengths are usually for the longest continuous river system, including major headstream tributaries, since that is how the longest-river rankings are conventionally measured. The named source reflects that longest measured headstream.

World Rivers Length Reference

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Ranking the world’s longest rivers is famously tricky because the source and mouth of a great river are both ambiguous. This reference lists the longest rivers by total length in kilometres and miles, with the source region, the sea or basin each drains into, and the continent.

How it works

Rivers are ranked by total length of the longest continuous river system, including major headstream tributaries — the convention used in longest-river tables. Each entry records:

Length — in kilometres and miles, converted at 1 km = 0.621371 mi.
Source — the headwater region where the longest measured branch begins.
Outflow — the sea, ocean, or basin the river drains into.
Continent — for grouping.

Because there is no single agreed way to pick a source or a mouth, figures differ between surveys, which is why the Nile and Amazon swap the top spot depending on the method.

Tips and notes

Length is not the same as size: the Amazon dwarfs every other river by discharge, carrying roughly a fifth of all river water reaching the oceans, even though its length is close to the Nile’s. Treat the figures here as widely cited estimates for ranking and comparison, and expect variation of tens to hundreds of kilometres between sources because of how sources and deltas are measured.