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.

US 31 continues due north through Lynnville, Columbia, Spring Hill, Franklin and Brentwood to Nashville.

At Exit 1 in Ardmore, it leaves I-65 and begins an unsigned concurrency with State Route 7.

In Columbia, US 31 picks up the names Carmack Boulevard and Garden Street; it also has a short concurrency with US 412 Business (US 412 Bus.)

After leaving Columbia, US 31 gains two designations, first it gains a Tennessee Parkway designation from Columbia to Rosa L. Parks Boulevard in Nashville, and then it picks up the hidden SR 6, which it keeps later as US 31E to the Tennessee state line.

US 31 goes through some more rural countryside before meeting the western terminus of SR 396 (Saturn Parkway) in Spring Hill and gains the name 1st Street.

US 31 then has an intersection with mainline US 431 (5th Avenue) before passing through Franklin Square and crossing the Harpeth River to meet SR 397 and the northern end of US 31 Truck.

US 31E then goes through Hendersonville, picks up the name Nashville Pike and has an incomplete interchange with SR 386 (Vietnam Veterans Parkway).