South Carolina Highway 340 (SC 340) is a 10.990-mile-long (17.687 km) state highway in the U.S. state of South Carolina.

The highway connects the Timmonsville area with Darlington.

It crosses over Jeffries Creek and High Hill Creek before entering the city limits of Darlington.

There, it intersects U.S. Route 52 (US 52; Governor Williams Highway).

It crosses some railroad tracks before it meets its northern terminus, an intersection with SC 34 (Pearl Street).