M-1, also known as Woodward Avenue, is a north–south state trunkline highway in the Metro Detroit area of the US state of Michigan. The highway, called "Detroit's Main Street", runs from Detroit north-northwesterly to Pontiac. It is one of the five principal avenues of Detroit, along with Michigan, Grand River, Gratiot, and Jefferson avenues. These streets were platted in 1805 by Judge Augustus B. Woodward, namesake to Woodward Avenue. The Federal Highway Administration (FHWA) has listed the highway as the Automotive Heritage Trail, an All-American Road in the National Scenic Byways Program. It has also been designated a Pure Michigan Byway by the Michigan Department of Transportation (MDOT), and was also included in the MotorCities National Heritage Area designated by the US Congress in 1998.

The State Trunkline Highway System consists of all the state highways in Michigan, including those designated as Interstate, United States Numbered, or State Trunkline highways. In their abbreviated format, these classifications are applied to highway numbers with an I-, US, or M- prefix, respectively. The system is maintained by the Michigan Department of Transportation (MDOT) and comprises 9,669 miles (15,561 km) of trunklines in all 83 counties of the state on both the Upper and Lower peninsulas, which are linked by the Mackinac Bridge. Components of the system range in scale from 10-lane urban freeways with local-express lanes to two-lane rural undivided highways to a non-motorized highway on Mackinac Island where cars are forbidden. The longest highway is nearly 400 miles (640 km) long, while the shortest is about three-quarters of a mile. Some roads are unsigned highways, lacking signage to indicate their maintenance by MDOT; these may be remnants of highways that are still under state control whose designations were decommissioned or roadway segments left over from realignment projects.