Denio is a census-designated place in Humboldt County, Nevada, along the Oregon state line in the United States. The Denio post office was originally north of the state line in Harney County, Oregon, but the residents moved the building into Nevada in the mid-20th century. 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.