Kuna is a city in Ada County, Idaho, United States. It is part of the Boise City?Nampa, Idaho Metropolitan Statistical Area. The population was 15,210 at the 2010 census.Kuna is one of the fastest-growing areas in Idaho, having nearly tripled in population between 2000 and 2010.Kuna is commonly misspelled and mispronounced as "Koona".