M-70 was a state trunkline highway in the US state of Michigan. In the 1920s, the highway originally connected Sterling in southwest Arenac County with Prescott in southeast Ogemaw County. The route was later adjusted to run from M-76 near Sterling along a convoluted route through Maple Ridge and Prescott to end at M-55 in Nester's Corners. The highway was still a gravel road when the designation was removed by 1960.
M-70 was first shown on a state map on July 1, 1919, with the debut of the Michigan state trunkline highway system. The original routing was shown between M-76 at Sterling and M-55 at Prescott. In 1929, M-55 was shifted to run due east from Selkirk to US Highway 23 north of Whittemore. The segment east of Prescott to Whittemore was turned over to the county, but the section north of Prescott was added to M-70. This extended M-70 north to its terminus in Nester's Corners. The designation was decommissioned by July 1, 1960. At the time, the highway was still a gravel road.