Denio is a census-designated place (CDP) that lies on the Nevada-Oregon state line in Humboldt County, Nevada, in the United States. There was formerly a Denio post office north of the state line in Harney County, Oregon. The population of the CDP, which is entirely in Nevada, was 47 at the 2010 census; additional development considered to be Denio extends into Oregon. The CDP includes a post office, a community center, a library, and the Diamond Inn Bar, the center of the town's social life.