Ogemaw County is a county located in the Lower Peninsula of the state of Michigan. As of the 2010 census, the population was 21,699. The county seat is West Branch.
The county was originally created in 1840, but was absorbed into Iosco County in 1867. It was later recreated in 1873 and finally organized in 1875. The county's name is an Anglicization of the Anishinaabemowin word ogimaa, meaning "chief".
The county has a total area of 575 square miles (1,490 km2), of which 563 square miles (1,460 km2) is land and 11 square miles (28 km2) (2.0%) is water.