Thorntown is a town in Sugar Creek Township, Boone County, Indiana, United States. The population was 1,520 at the 2000 census. Thorntown is located in northwestern Boone City, about halfway between Lafayette and Indianapolis.
Thorntown is located at 40°7′44″N 86°36′32″W / 40.12889°N 86.60889°W / 40.12889; -86.60889 (40.128757, -86.608762).
According to the United States Census Bureau, the town has a total area of 0.6 square miles (1.5 km²), all of it land.