U.S. Route 25 or U.S. Highway 25 (US 25) is a north–south United States Numbered Highway that runs for 750 miles (1,210 km) in the Southern and Midwestern U.S. Its southern terminus is in Brunswick, Georgia, from where it proceeds mostly due north, passing through the cities of Augusta, Georgia; Greenville, South Carolina; and Asheville, North Carolina, before dividing into two branches, known as US 25W and US 25E between Newport, Tennessee, and North Corbin, Kentucky. After passing through Richmond and Lexington, Kentucky, it reaches its northern terminus at Ohio state line in Covington, Kentucky. The route is an important crossing of the Appalachian Mountains, and it is covered by three of the corridors of the Appalachian Development Highway System (ADHS). When the highway was originally established in 1926, the route extended from North Augusta, South Carolina, to Port Huron, Michigan. The southern end was extended to its current terminus in 1936, while the northern end was truncated in 1974.

The United States Numbered Highway System is an integrated network of roads and highways numbered within a nationwide grid in the contiguous United States. As the designation and numbering of these highways were coordinated among the states, they are sometimes called Federal Highways, but the roadways were built and have always been maintained by state or local governments since their initial designation in 1926.