Río Lavayén winds through the subtropical lowlands of Jujuy Province in northwestern Argentina, flowing as a tributary of the Río San Francisco system. The river passes through a region of remarkable biodiversity, where the transition between the Yungas cloud forest and the Chaco lowlands creates a rich aquatic environment. Its waters support a variety of native warmwater species that attract local anglers and visiting sport fishermen alike, making it one of the more notable fishing destinations in the province.