Oark is an unincorporated community and census-designated place in Johnson County, Arkansas, United States. Oark is located on Arkansas Highway 215, 16 miles northwest of Clarksville. It was first listed as a CDP in the 2020 census with a population of 43.Oark has a post office with ZIP Code 72852. The community is surrounded by the Ozark National Forest with the scenic Mulberry River nearby.