Genesee County is a county in the U.S. state of Michigan. As of the 2010 census, the population was 425,790. The county seat and population center is Flint.  It is the state's fifth most populous county.

It was created on March 28, 1835 and fully organized on April 4, 1836. It was named after Genesee County, New York by settlers from New York. Many local place names in the county are also from New York and Pennsylvania, reflecting the pattern of settlement. A major attraction for visitors is Crossroads Village, a living history village north of Flint.

Genesee is noted for having had the fossil of an ancient whale known as Balaenoptera Lacepede unearthed in Thetford Township during quarry work and estimated at 11,000 years old.