Flathead County is a county located in the U.S. state of Montana. At the 2020 census, its population was 104,357, making it the state's fourth most populous county. Its county seat is Kalispell. Its numerical designation is 7. Its northern border is on the state's north border, making it contiguous with the Canada–US border, facing British Columbia. Flathead County comprises the Kalispell, Montana Micropolitan Statistical Area, with neighboring Lake County following soon after.