Green Lake County is a county located in the U.S. state of Wisconsin. As of the 2020 census, the population was 19,018. Its county seat is Green Lake. In 2020, the center of population of Wisconsin was located in Green Lake County, near the city of Markesan.

Green Lake is a city in and county seat of Green Lake County, Wisconsin, United States. The city had a population of 1,001 in the 2020 census. It is located on the north side of Green Lake. The Town of Green Lake is located on the south side of Big Green Lake, opposite the city.