Bay City is a city and county seat of Bay County in the U.S. state of Michigan, located near the base of the Saginaw Bay on Lake Huron. As of the 2010 census, the city's population was 34,932, and it is the principal city of the Bay City Metropolitan Statistical Area, which is included in the Saginaw-Midland-Bay City Combined Statistical Area. The city, along with nearby Midland and Saginaw, form the Greater Tri-Cities region of Central Michigan.