What is the name of world's second-longest river?

The Amazon River in South America is the largest river by discharge volume of water in the world, and the second-longest river in the world.

The headwaters of the Apurímac River on Nevado Mismi had been considered for nearly a century as the Amazon's most distant source until a 2014 study found it to be the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru. The Mantaro and Apurímac rivers join, and with other tributaries form the Ucayali River, which in turn meets the Marañón River upstream of Iquitos, Peru, forming what countries other than Brazil consider to be the main stem of the Amazon.

The Amazon River of South America is the second-longest river in the world with a length of 6,400 km. But it is by far the largest river by water flow with an average discharge greater than the next seven largest rivers combined. It flows through Brazil, Peru, Bolivia, Colombia, Ecuador, Venezuela, and Guyana.