U.S. Route 1 or U.S. Highway 1 (US 1) is a major north–south United States Numbered Highway that serves the East Coast of the United States. It runs 2,370 miles (3,810 km) from Key West, Florida, north to Fort Kent, Maine, at the Canadian border, making it the longest north–south road in the United States. US 1 is generally paralleled by Interstate 95 (I-95), though US 1 is significantly farther west and inland between Jacksonville, Florida, and Petersburg, Virginia, while I-95 is closer to the coastline. In contrast, US 1 in Maine is much closer to the coast than I-95, which runs farther inland than US 1. The route connects most of the major cities of the East Coast from the Southeastern United States to New England, including Miami, Jacksonville, Augusta, Raleigh, Richmond, Washington, D.C., Baltimore, Philadelphia, Newark, New York City, New Haven, Providence, Boston, and Portland.

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.