Berlin is a city in Green Lake and Waushara counties in the U.S. state of Wisconsin. The population was 5,571 at the 2020 census. Of this, 5,435 were in Green Lake County, and only 89 were in Waushara County. The city is located mostly within the Town of Berlin in Green Lake County, with a small portion extending into the Town of Aurora in Waushara County.

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.