Lakeside is an unincorporated area and census-designated place (CDP) in Flathead County, Montana, United States. The population was 2,705 at the 2020 census, up from 2,669 in 2010.

Flathead County is 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.