Interstate 26 (abbreviated I-26) is an east-west main route of the Interstate Highway System in the Southeastern United States. I-26 runs from the junction of U.S. Route 11W and U.S. Route 23 in Kingsport, Tennessee, generally south and southeast to U.S. Route 17 in Charleston, South Carolina. The portion from Mars Hill, North Carolina, east (compass south) to Interstate 240 in Asheville, North Carolina, is signed as Future I-26 because it does not yet meet Interstate standards; a short realignment is also planned in Asheville.

Prior to August 5, 2003, the western terminus was at Interstate 40 and Interstate 240 southwest of Asheville. At that time, the final section of freeway in North Carolina, from Mars Hill north to the Tennessee state line, replaced the old two-lane U.S. Route 23. I-26 was extended into Tennessee on the US 23 freeway, taking over approximately half of the former Interstate 181 from U.S. Route 321/State Route 67 in Johnson City, Tennessee, to Interstate 81 south of Kingsport, Tennessee. The American Association of State Highway and Transportation Officials denied an extension of I-26 along the remainder of I-181 to Kingsport, since it would give a main interstate route a stub end (not connecting to another interstate). The extension was finally achieved by the Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users, signed into law August 10, 2005. Thus I-26 now ends about two miles (3 km) south of the Virginia state line, and the freeway continues to the state line as US 23.

North of Kingsport, US 23 continues north to Portsmouth, Ohio, as Corridor B of the Appalachian Development Highway System, and beyond to Columbus, as Corridor C. In conjunction with the Columbus-Toledo corridor formed by US 23, State Route 15 and Interstate 75, I-26 forms part of a mostly high-speed four-lane highway from the Great Lakes to the Southeast. There are no plans for further I-26 extensions into Virginia, Kentucky and farther north.

I-26 map