Interstate 526 (abbreviated I-526) or the Mark Clark Expressway is a beltway, Interstate Highway of Interstate 26 in Berkeley and Charleston counties in South Carolina, USA.

Interstate 526 forms a 19.26-mile (31.00 km) half-circle around the historic peninsular and West Ashley portions of the City of Charleston with the western terminus at U.S. Highway 17 west of the Ashley River, and the eastern terminus is at U.S. Highway 17, near Mt.Pleasant. Interstate I-26 and U.S. Highway 52/78 intersect with Interstate 526 in the City of North Charleston, South Carolina. There have been attempts to complete I-526 across Johns Island (to meet SC 30) as originally planned so that it will form three fourths of a circle around Charleston but each attempt has failed due to lack of credible funding and vocal opposition.

South Carolina Highway 30 is an orphaned segment of Interstate 526. Approximately 10 miles (16 km) separate the eastern terminus of I-526's current extent from the eastern terminus of SC 30. The mileage markers and exit numbers on both SC 30 and I-526 are based on an eventual merging of the routes: with miles 1 to 3 occurring on SC 30 and miles 10 to 30 used on the current I-526 route.

I-526 crosses the Cooper River via the Don N. Holt Bridge, the Wando River over the James B. Edwards Bridge, and the Ashley River by way of the General William C. Westmoreland Bridge.

I-526 has been built in several phases starting in the early 1980s, with the highway being finished to US 17 in Mount Pleasant in 1998.

Interstate 526 is proposed to be completed from US Route 17 onto Johns Island and James Island across SC 171, bridges over the Stono River to Johns Island. SC 30 will be decommissioned. Interstate 526 would go thru Mount Pleasant, North Charleston, Charleston, Johns Island and James Island. In 2009, the Town of James Island passed a resolution opposing the building of I-526 across any part of the town. A small group of residents, the Coastal Conservation League as well as a grassroots group, called Nix 526, are voicing opposition to the proposed road. The majority of Charleston residents as polled in 2012, support completion of the road.

After I-526 goes over U.S. Highway 17 at its eastern terminus in Mount Pleasant, the route continues as Business Spur 526. Business 526 is named Chuck Dawley Boulevard, a surface street, and terminates at its junction with South Carolina Highway 703 (Ben Sawyer Boulevard). This street was formerly the eastern part of Coleman Boulevard and was U.S. Route 17-701 Business. Coleman Boulevard continues westward from the junction of SC 703 until its intersection with US 17 near the Cooper River Bridge. Although Business 526 travels toward the southwest from the I-526 terminus, it is still signed east–west, corresponding with I-526.