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 La…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. The city had a population of 107,395 at the 2020 census, making it the third-most populous city in Wisconsin, after Milwaukee and Madison, and the third-most populous city on Lake Michigan, after Chicago and Milwaukee. It is the principal city of the Green Bay metropolitan area, which covers Brown, Kewaunee, and Oconto counties and had a population of 320,050 in 2020.