Interstate 77 (abbreviated I-77) is an Interstate Highway in the eastern United States. It traverses diverse terrain, from the mountainous state of West Virginia to the rolling farmlands of North Carolina and Ohio. It largely supplants the old U.S. Route 21 between Cleveland, Ohio, and Columbia, South Carolina, as an important north–south corridor through the middle Appalachians. The southern terminus of Interstate 77 is in Columbia at the junction with Interstate 26. The northern terminus is in Cleveland at the junction with Interstate 90.

The East River Mountain Tunnel, connecting Virginia and West Virginia, is one of only two instances in the United States where a mountain road tunnel crosses a state line. The other is the Cumberland Gap Tunnel, connecting Tennessee and Kentucky.

I-77 begins as a eight-lane highway at I-26 in the far southeastern part of the Columbia metropolitan area. The Columbia skyline is visible from this interchange. In the Columbia area, I-77 offers easy access to Fort Jackson before meeting I-20 in the northeastern part of the city. This segment of I-77, combined with I-20 and I-26, form a beltway around Columbia, though it is not officially designated as such. In the Columbia area, the control city for northbound traffic is Charlotte, N.C., while the control city for southbound traffic is Charleston, S.C and Spartanburg, S.C. from Exit 9 to I-26.