United States Highway 112 is a designation, defunct since 1961, for a largely east-west highway in the south of the U.S. state of Michigan between New Buffalo, Michigan and Ypsilanti, Michigan having its old termini at intersections with the original U.S. Highway 12. It was also the designation of the Detroit Industrial Freeway which was later designated Interstate 94, the old "U.S. 112" designation becoming superfluous east of Ypsilanti. Part of old U.S. 112 was the Old Sauk Trail, an Indian trail. All of it, except for a bypass of Niles undivided surface road. It passes through terrain full of lakes suitable for recreational use.

It intersects Interstate 94 east of New Buffalo; U.S. Highway 31 west of Niles, U.S. Highway 131 in White Pigeon; Interstate 69 just east of Coldwater; U.S. Highway 127 near Somerset Center, U.S. Highway 23 east of Saline; and Interstate 94 west of Ypsilanti.

Michigan designates this highway the Pulaski Memorial Highway in honor of the Polish Count Casimir Pulaski, a hero of the American War of Independence.

In 1961 Michigan completed Interstate 94 between New Buffalo and Ypsilanti along the corridor of the old, more northerly and urban, U.S. 12 to the north and removed signs for U.S. 12 parallel to and along the freeway. Michigan redesignated the intrastate U.S. 112 as U.S. 12, which has been little altered since 1961 except to give access to new freeways. U.S. 112 was a heavily-traveled alternative to the more urban U.S. 12 in the pre-Interstate era between Detroit and Chicago. West of Sturgis it (now US 12) is very lightly traveled due to the nearby Indiana Toll Road. Generally flat but curvy west of Coldwater, it passes through the scenic Irish Hills east of Coldwater.

In 1926, U.S. 112 was originally designated to contain none of the old Detroit-Ypsilanti segment; somewhere between Edwardsburg and Adamsville it made a sharp turn to the southwest along what are now Michigan State Highway 205, Indiana State Highway 19 , and Indiana State Highway 112 to connect to U.S. Highway 20 west of Elkhart, Indiana.

As part of the shortest route between Detroit and Chicago, it was considered a likely corridor for an expressway along its route before the Indiana Toll Road and Interstate 94 made such a highway largely unnecessary.