Flatside Wilderness is a 9,507-acre protected area in Arkansas in the Ouachita Mountains and the easternmost of the six wilderness areas in the Ouachita National Forest. Established in 1984 and later enlarged in 2019 by the addition of Bethune Woods, it is both a significant conservation area and a destination for hiking and backcountry travel, with part of the Ouachita National Recreation Trail crossing it. Its character comes from long sandstone ridges, steep relief, forested summits, and clear streams, including Cedar Creek and Crystal Prong. White Oak Mountain, Crystal Mountain, Grindstone Mountain, and Forked Mountain help define a landscape shaped by slow-eroding Jackfork Sandstone above Stanley Shale.