The Gregório River is a river of Amazonas and Acre states in western Brazil. It is a tributary of Juruá River.

Course

The Gregório River runs in a northeast direction through the Brazilian states of Acre and Amazonas. It has a length total of 350 km. In Acre between the BR-364 highway and the Amazonas border the river forms the boundary between the 216062 ha Rio Gregório State Forest to the east and the 143897 ha Mogno State Forest to the west, two sustainable use conservation units created in 2004. Across the border in Amazonas the river runs through the 427,004 ha Rio Gregório Extractive Reserve, which protects 80% of the sources of the river.