Lake County is a county located in the northwest part of the U.S. state of Montana. As of the 2020 census, the population was 31,134. Its county seat is Polson.

Polson is a city in , United States, on the southern shore of Flathead Lake and within the Flathead Indian Reservation. The population was 5,148 at the 2020 census. It is the county seat of Lake County. In 1898 the city was named after pioneer rancher David Polson. It was incorporated in 1910.