Ortonville is a city located in Minnesota at the southern tip of Big Stone Lake, along the border with South Dakota. As of the 2000 census, the city had a total population of 2,158. It is the county seat of Big Stone County6. Big Stone Lake State Park is nearby.
According to the United States Census Bureau, the city has a total area of 8.9 km2 (3.5 mi2). 8.8 km2 (3.4 mi2) of it is land and 0.1 km2 (0.1 mi2) of it is water. The total area is 1.45% water.