Spencer is a city in McCook County, South Dakota, United States. The population was 154 at the 2010 census. The city was almost completely destroyed by a violent F4 tornado on May 30, 1998 which killed 6.
Spencer is located at 43°43′40″N 97°35′31″W / 43.72778°N 97.59194°W / 43.72778; -97.59194 (43.727853, -97.592033).
According to the United States Census Bureau, the city has a total area of 0.3 square miles (0.7 km²), all of it land.