Yonna is an unincorporated community in Klamath County, Oregon, United States. It lies east of Oregon Route 140 in Yonna Valley, northeast of Dairy and near the base of Short Lake Mountain.
At one time known as Alkali Valley, the area is now known by its Klamath name, Yonna Valley. According to Oregon Geographic Names, the name may come from yana, meaning "below" as in the valley, or it may derived from yaina, meaning "mountain". A post office was established in Yonna Valley in 1906. It closed in 1913.