M-123 is a 95-mile-long (154-km.) paved road in the eastern Upper Peninsula of the U.S. state of Michigan. From west to east, it extends from M-28 near Newberry to I-75 exit 352 near St. Ignace, Michigan. It is a Scenic Heritage Route within the Michigan Heritage Route system.

M-123 serves a thinly-populated section of the state. Much of the highway passes through the eastern unit of the Hiawatha National Forest. It is the only paved road serving Tahquamenon Falls State Park and the Whitefish Point region.

Michigan state highways | Upper Peninsula of Michigan