Mountain Fork, also known as the Mountain Fork of the Little River, is a 98-mile-long (158 km) tributary of the Little River in western Arkansas and southeastern Oklahoma in the United States. Via the Little and Red rivers, it is part of the watershed of the Mississippi River. The stream rises in the Ouachita Mountains. Broken Bow Lake is an artificial lake along the course of the Mountain Fork. The stream is known for canoeing, kayaking, and sport fishing, including for stocked trout.

The Ouachita National Forest is a vast congressionally-designated National Forest that lies in the western portion of Arkansas and portions of extreme-eastern Oklahoma, USA.