Onamia (/oʊˈneɪmiːə/ oh-NAYM-ee-ə)[5] is a city in Mille Lacs County, Minnesota, United States.

Originally, the city of Onamia was organized from the merger of two communities, the village of Onamia (Ojibwe: Onamanii-zaaga'iganiing) and the village of Ericksonville (Ojibwe: Gibaakwa'igaansing).

Onamia is in northern Mille Lacs County, on the south shore of Lake Onamia and 3 miles (5 km) south of Mille Lacs Lake.

U.S. Route 169 passes through the east side of the city, leading south 22 miles (35 km) to Milaca, the county seat, and north 20 miles (32 km) to Garrison on the northwest shore of Mille Lacs Lake.

State Highway 27 passes through Onamia as its Main Street, leading northeast 12 miles (19 km) to Isle at the southeast end of Mille Lacs Lake, and west 40 miles (64 km) to Little Falls on the Mississippi River.

Mille Lacs Kathio State Park is 4 miles (6 km) northwest of the city.

Sections of the Rum River State Forest are located nearby.

46.4% of all households were made up of individuals, and 26.7% had someone living alone who was 65 years of age or older.

42.8% of all households were made up of individuals, and 23.9% had someone living alone who was 65 years of age or older.