    this is a list of the longest rivers on earth. it includes river systems over 1,000 kilometers. ==definition of length== there are many factors, such as the source, the identification or the definition of the mouth, and the scale of measurementfor more on this, see coastline paradox of the river length between source and mouth, that determine the precise meaning of "river length". as a result, the length measurements of many rivers are only approximations. in particular, there has long been disagreement as to whether the nile or the amazon is the world's longest river. the nile has traditionally been considered longer, but in recent years some brazilian and peruvian studies have suggested that the amazon is longer by measuring the river plus the adjacent parÃ¡ estuary and the longest connecting tidal canal. for the purpose of determining maximum length a river's "true source" is considered to be the source of whichever tributary is farthest from the mouth. this tributary may or may not have the same name as the main stem river. for example, the source of the mississippi river is normally said to be lake itasca in the u.s. state of minnesota, but the most distant source in the mississippi system is that of the jefferson river in the state of montana, a tributary of the missouri river which in turn is a tributary of the mississippi. when the mississippi is measured from mouth to this farthest source, it is called the mississippiâmissouriâjefferson.  furthermore, it is sometimes hard to state exactly where a river begins, especially rivers that are formed by ephemeral streams, swamps, or changing lakes. in this article, length means the length of the longest continuous river channel in a given river system, regardless of name.  the mouth of a river is hard to determine in cases where the river has a large [[e
Lists_by_length Lists_of_rivers