What negro river is a tributara of what major south America river?

The Negro River (Portuguese: Rio Negro, Spanish: Río Negro) is a major tributary of the Amazon River of South America.

It is an immense blackwater body and one of the world's longest blackwater rivers.

The 2,200 kilometre Negro River originates in southern Colombia before traversing northwest Brazil then flowing to its confluence with the Solimoes (upper Amazon) River where the two merge at Manaus city in Brazil's biggest state, Amazonas.