Araguay, Or Aragnaya, a river of Brazil, rises in lat. 18° 10' S. and lon. 51° 30' W., flows northward, between the provinces of Matto Grosso and Goyaz, to Sao Joao, lat. 6° 5' S., where it unites with the Tocantins, and the combined stream discharges its waters, after a course of nearly 400 m. further, into the southern estuary of the Amazon, in lat. 1° 40' S, Its whole course is about 1,300 m., of which about 1,100 are navigable. About midway in its course it separates into two arms, which enclose the island of Banana or Santa Anna, 210 m. long and 40 broad. Its principal tributary is Das Mortes, which joins it in lat. 12° S. Many tribes of warlike savages are found on the banks of the Aragtiay. It furnishes an uninterrupted navigation from Para almost to the head waters of the Parana.