M-102 is a state trunkline highway in the US state of Michigan that runs along the northern boundary of Detroit following 8 Mile Road. The highway follows the Michigan Baseline, a part of the land survey of the state, and the roadway is also called Base Line Road in places. As a county road or city street, 8 Mile Road extends both east and west of the M-102 designation, which leaves 8 Mile on the eastern end to follow Vernier Road. The western terminus of M-102 is at the junction of 8 Mile Road and M-5 and the opposite end is at Vernier Road and Interstate 94. The 8 Mile Road name extends west to Pontiac Trail near South Lyon with a discontinuous segment located west of US Highway 23. The eastern end of 8 Mile Road is in Grosse Pointe Woods near I-94.
The highway was first designated in the late 1920s, connecting US Highway 10 with US 25. Extensions to the highway designation moved the termini in the 1930s and 1940s east to M-29 and US 16. A change in the 1960s added a section of north–south roadway to the eastern end of M-102; that change was reversed within about a year. A western extension along Grand River Avenue in 1977 was reversed in 1994, and M-102 has remained the same since.