M-154 is a state trunkline highway in the U.S. state of Michigan. It is entirely on Harsens Island at the mouth of the St. Clair River. It is one of only three trunklines in Michigan on islands. The other two are M-134 on Drummond Island and M-185 on Mackinac Island. Access to Harsens Island and M-154 is provided by ferry which runs year round. The highway was first designated in 1931, and realigned on the island within the next two years.