Tuscola County is a county in the Thumb region of the U.S. state of Michigan. As of the 2020 census, the population was 53,323. The county seat is Caro. The county was created by Michigan Law on April 1, 1840, from land in Sanilac County and attached to Saginaw County for administrative purposes. The Michigan Legislature passed an act on March 2, 1850, that empowered the county residents to organize governmental functions.

The Thumb is a region and a peninsula of the U.S. state of Michigan, so named because the Lower Peninsula is shaped like a mitten. The Thumb area is generally considered to be in the Central Michigan region, east of the Tri-Cities and north of Metro Detroit. The region is also branded as the Blue Water Area.