Shiawassee County is a county located in the U.S. state of Michigan. As of the 2020 United States Census, the population was 68,094. The county seat is Corunna, and the largest city in the county is Owosso. In 2010, the center of population of Michigan was located in Shiawassee County, in Bennington Township.

Owosso is the largest city in Shiawassee County in the U.S. state of Michigan. The population was 14,714 at the 2020 census. The city is mostly surrounded by Owosso Township on its west, but the two are administered autonomously. The city was named after Chief Wosso, an Ojibwe leader of the Shiawassee area.