Denio is a census-designated place 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. Recreational activities available in the Denio area include fishing, opal mining, rockhounding, hunting, and visiting the hot springs. The Humboldt County School District operates the Denio School, a kindergarten-eighth grade school, on the Nevada side of the state line.Denio Junction is about two miles south of Denio, at the junction of State Route 140 and State Route 292.