The Rio Negro (Portuguese: Rio Negro [ˈʁi.u nɛɡɾu]; Spanish: Río Negro [ˈri.o ˈneɣɾo] "Black River") is the largest left tributary of the Amazon River, the largest blackwater river in the world (accounting for about 14% of the water in the Amazon basin),[4] and one of the world's ten largest rivers by average discharge.