Langdon is a city in Cavalier County, North Dakota, in the United States. It is the county seat of Cavalier County. The population was 1,878 at the 2010 census. Langdon was incorporated in 1885 but was designated as the county seat in 1884.
Langdon is located at 48°45′42″N 98°22′18″W / 48.76167°N 98.37167°W / 48.76167; -98.37167 (48.761696, -98.371780).
According to the United States Census Bureau, the city has a total area of 1.7 square miles (4.5 km²), of which, 1.7 square miles (4.4 km²) of it is land and 0.04 square miles (0.1 km²) of it (1.72%) is water.