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.

Ouachita Baptist University (OBU) is a private Baptist university in Arkadelphia, Arkansas. The university's name is taken from the Ouachita River, which forms the eastern campus boundary. It is affiliated with the Arkansas Baptist State Convention, a state convention affiliated with the Southern Baptist Convention.