Longest river tributary

Longest river tributary
Who
Madeira tributary
What
3380 kilometre(s)
When
01 January 0001
The largest river basin in the world is that drained by the Amazon, which covers about 7,045,000 km² (2,720,000 miles²). It has countless tributaries, including the Madeira, which at 3,380 km (2,100 miles) is the longest tributary in the world, being surpassed by only 17 other rivers.