Interstate 26 is a South Carolina Interstate highway running generally east–west from Landrum, in Spartanburg County, to U.S. Route 17, in Charleston, South Carolina. It is also the longest interstate highway in South Carolina.

Beginning in the city of Charleston, I-26 travels northwestwardly over flat plains with little urbanization past Summerville. After the junction with I-95 just inside of Orangeburg County, the terrain becomes somewhat hilly. Orangeburg is the first major stop outside Charleston with several exits bearing this name. Between Orangeburg and the junction with Interstate 77 just outside of Cayce the highway goes up and down a few very long hills averaging about 100 feet (30 m) or 30 meters high.[citation needed] Beyond Interstate 77 is the Columbia metropolitan area with lodging, dining, and shopping possibilities. This metropolitan area ends mostly after exit 101, past which the terrain becomes somewhat hilly once again. The next city is Spartanburg, where I-26 has a junction with the Interstate 85 corridor, which has a significant amount of international business and manufacturing. The 11-mile (18 km) section of I-26 from Interstate 126 in Columbia to US 176 at Exit 97 was the first section of the highway to open up to traffic (on September 7, 1960).

Construction of I-26 began in the late-1950s in the Columbia area and proceeded in stages heading both west up towards Greenville and east towards Charleston. The highway was largely completed from Columbia to North Charleston by 1964; the section from Aviation Avenue to the highway's terminus at US 17 in downtown Charleston progressed slower due to land takings for the right of way and numerous bridges and viaducts that had to be built and thus was not completed until 1969.