Lakeside is an unincorporated area and census-designated place (CDP) in Flathead County, Montana, United States. The population was 2,669 at the 2010 census, up from 1,679 in 2000.
Lakeside is located in southern Flathead County at 48°1′12″N 114°13′41″W (48.019933, -114.228152), on the western shore of the north end of Flathead Lake. It is bordered to the north by Somers, and it extends south as far as the Lake County line. U.S. Route 93 passes through Lakeside, leading north 14 miles (23 km) to Kalispell and south 37 miles (60 km) to Polson at the south end of Flathead Lake.
According to the United States Census Bureau, the Lakeside CDP has a total area of 18.0 square miles (46.5 km2), of which 14.1 square miles (36.4 km2) is land and 3.9 square miles (10.1 km2), or 21.69%, is water.
As of the census of 2000, there were 1,679 people, 705 households, and 520 families residing in the CDP. The population density was 228.9 people per square mile (88.3/km2). There were 956 housing units at an average density of 130.3 per square mile (50.3/km2). The racial makeup of the CDP was 97.92% White, 0.06% African American, 0.71% Native American, 0.42% Asian, 0.30% from other races, and 0.60% from two or more races. Hispanic or Latino of any race were 1.07% of the population. 15.6% were of English, 15.3% German, 14.8% Norwegian, 8.2% United States or American, 7.3% Irish and 5.5% Italian ancestry according to Census 2000.
There were 705 households, out of which 26.0% had children under the age of 18 living with them, 67.7% were married couples living together, 3.8% had a female householder with no husband present, and 26.2% were non-families.