Green Bay is a city in Brown County, Wisconsin, United States, and its county seat. It is located at the head of Green Bay, a sub-basin of Lake Michigan at the mouth of the Fox River. Green Bay had a population of 107,395 at the 2020 census, making it the third-most populous city in Wisconsin and the third-most populous city on Lake Michigan. The Green Bay metropolitan area covers Brown, Kewaunee, and Oconto counties and had a population of 320,050 in 2020.