The length of a river is measured from its source to its mouth. The longest river is the Nile-Kagera which is at least 6,650 Km long. The Reprua is a river in the Gagra District of Abkhazia which is only 18 meters long. It is possibly the shortest named river in the world.
A river can be as long as a country! For example the Mississippi River is almost as long as the U.S vertically.
The river Alt is 28kilometers long.
The Charles River is about 81mi long.
The Missouri River is 2,341 miles long and is the longest tributary to the Mississippi River.
The River Wharfe is a river in Yorkshire, England and is 60 miles long.
the river nile it is 6695 km long
The river Thames is 215 miles long, the longest is the river Severn at 220 miles long.
the river medway is 70 miles long (113km) Very long I know
The Benue River Is 1400 Km Long
River crouch is 17.5 miles long
The Ebro river is 298 km long.
The Roe River is 12.6 meters long!