| State: | MI |
| Type: | M 1973 |
| Route: | 147 |
| Map Custom: | yes |
| Map Notes: | M-147 highlighted in red |
| Length Mi: | 0.505 |
| Length Ref: | [1] |
| Established: | 1936 |
| Decommissioned: | January 5, 1991[2] |
| Direction A: | West |
| Terminus A: | near Jackson |
| Direction B: | East |
| Terminus B: | State Prison of Southern Michigan |
| Counties: | Jackson |
| Previous Type: | M |
| Previous Route: | 146 |
| Next Type: | M |
| Next Route: | 149 |
M-147 was a state trunkline highway in the U.S. state of Michigan. The route started at M-106 just north of Jackson and stopped at the entrance of State Prison of Southern Michigan. The route of M-147 was transferred to local control in 1991 after being signed originally in 1936.
M-147 started at an intersection with M-106 west of the State Prison of Southern Michigan property. From there, the trunkline ran about a half mile (0.8 km) due east to the prison gate and terminated. Just east of the terminus was a branch line of the Grand Trunk Western Railroad.[3] In 1976, a newspaper article said that "it's ... the second shortest highway on Michigan's state highway system, but for those who travel it one way, M-147 is the longest road in the world" in discussing its role as the connection to the state prison,[4] the world's largest walled prison.[5] Another in 1972, called it a "snippet of highway" that "most people hope they never have to travel" in a profile of short highways to "important places".[6]
M-147 was designated in 1936 to connect the prison property with the state trunkline system.[7] [8] It would remain under state control until January 5, 1991 when it was turned over to Jackson County.[2]