Clark County is a county located in the south-central part of the U.S. state of Arkansas. As of the 2020 census, the population was 21,446. The county seat is Arkadelphia. The Arkadelphia, AR Micropolitan Statistical Area includes all of Clark County.

Arkadelphia is a city in Clark County, Arkansas, United States. As of the 2020 census, the population was 10,380. The city is the county seat of Clark County. It is situated at the foothills of the Ouachita Mountains. Two universities, Henderson State University and Ouachita Baptist University, are located here. Arkadelphia was incorporated in 1857.