Onamia is a city in Mille Lacs County, Minnesota, United States. The population was 784 as of the 2020 census, down from 878 in 2010. U.S. Highway 169 and Minnesota State Highway 27 are the main routes in the community.

Mille Lacs County is a county in the East Central part of the U.S. state of Minnesota. As of the 2020 census, the population was 26,459. Its county seat is Milaca. The county was founded in 1857, and its boundary was expanded in 1860.