M-140 is a north–south state trunkline highway in Berrien and Van Buren counties of the US state of Michigan. The highway starts in the Niles area at M-139 and runs north through Watervliet to South Haven, ending at Interstate 196/US Highway 31 (I-196/US 31). In between, it runs through farm fields and past lakes in the southwestern part of the Lower Peninsula. The trunkline is used, on average, by between 1,500 and 10,200 vehicles.