The Agusan River is third longest river in the Philippines, located in the north-eastern part of Mindanao island, draining majority of the Caraga region and some parts of Davao de Oro.

It is the country's third largest river (after the Cagayan River and Rio Grande de Mindanao) with a total drainage area of 11,937 square kilometres (4,609 sq mi)[2] and an estimated length of 349 kilometres (217 mi) from its origin.

The marsh serves a flood retention basin for the Agusan River, cutting the high discharge of water causing flash floods in the lower reaches of the river.

Aside from that, the marsh harbors unique and pristine habitats like the sago and peat swamps forest and is a home to endangered and endemic flora and fauna.

As a consequence, it was designated a wildlife sanctuary by then-President Fidel V. Ramos in 1996.