Clarendon, county, central South Carolina, U.S. It consists of a low-lying region on the Coastal Plain that includes large areas of swampland. Lake Marion, formed by the Santee Dam on the Santee River, constitutes the western and southern border, and the county is also drained by the Black River. Santee National Wildlife Refuge is on Lake Marion, a popular attraction for fishing enthusiasts. At the northern tip of Clarendon county is Woods Bay State Park, featuring a large Carolina bay (an isolated swampy area) inhabited by alligators.

In 2019, Clarendon County, SC had a population of 34k people with a median age of 45.1 and a median household income of $40,900. Between 2018 and 2019 the population of Clarendon County, SC declined from 34,017 to 33,957, a −0.176% decrease and its median household income grew from $37,525 to $40,900, a 8.99% increase.

98.6% of the residents in Clarendon County, SC are U.S. citizens.

In 2019, the median property value in Clarendon County, SC was $102,000, and the homeownership rate was 77%. Most people in Clarendon County, SC drove alone to work, and the average commute time was 28.3 minutes. The average car ownership in Clarendon County, SC was 2 cars per household.

Clarendon County, SC borders Berkeley County, SC, Calhoun County, SC, Florence County, SC, Orangeburg County, SC, Sumter County, SC, and Williamsburg County, SC.