The following highways are/were numbered 931:
| Preceded by 930 | Lists of highways 931 | Succeeded by 932 |
U.S. Route 31 (US 31) is a part of the United States Numbered Highway System that runs from Spanish Fort, Alabama, to Mackinaw City, Michigan. It enters the U.S. state of Indiana via the George Rogers Clark Memorial Bridge between Louisville, Kentucky, and Clarksville, Indiana. The 266.02 miles (428.12 km) of US 31 that lie within Indiana serve as a major conduit. Some of the highway is listed on the National Highway System. Various sections are rural two-lane highway and urbanized four- or six-lane divided expressway. The northernmost community along the highway is South Bend near the Michigan state line.
