River, central Peru. Rising in the
Andes Mountains, it is part of the headwaters of the
Amazon River. It flows northwest at elevations of about 12,000 ft (3,650 m) and descends through jungles in unnavigable rapids and falls; emerging from the most spectacular of these rapids, the Pongo de Manseriche, it is only 575 ft (175 m) above sea level. For the rest of its 879-mi (1,415-km) course, it meanders eastward, receiving the
Huallaga River and then joining the
Ucayali River to form the Amazon.
For more information on Marañón River, visit Britannica.com.