Ocós is a municipality located in the San Marcos Department of Guatemala. It is situated on the Pacific Ocean coast at an altitude of approximately 4 meters (13 feet), positioned very close to the border with Mexico.
The municipality is characterized by its proximity to two major rivers, the Suchiate and the Naranjo. On January 23, 2014, Ocós lost about two-thirds of its territory when La Blanca was officially designated as the thirtieth municipality of the San Marcos Department.