M-72 is a state trunkline highway in the US state of Michigan, running from Lake Huron to Lake Michigan across the northern part of the Lower Peninsula. The highway connects M-22 in Empire with US Highway 23 (US 23) in Harrisville. It is one of only three Michigan state trunklines that cross the Lower Peninsula, shore to shore. In between, M-72 runs across Northern Michigan woodland, agricultural areas of the Leelanau Peninsula near Traverse City, and the Au Sable River watershed. The trunkline also provides access to Camp Grayling, a National Guard training facility near the city of the same name. Traffic levels along the highway vary from approximately 800 vehicles a day on the east end to over 32,000 vehicles near Traverse City.