Sullivan is a city in Hamilton Township, Sullivan County, Indiana, United States. The population was 4,249 at the 2010 census. It is part of the Terre Haute Metropolitan Statistical Area. The city is the county seat of Sullivan County. The town is served by the Southwest School Corporation, and students go to Sullivan High School.
Sullivan is located at 39°5′49″N 87°24′23″W / 39.09694°N 87.40639°W / 39.09694; -87.40639 (39.096888, -87.406447).
According to the United States Census Bureau, the city has a total area of 1.9 square miles (5.0 km²), all of it land.