Crestline is a village in Crawford and Richland Counties in the U.S. state of Ohio. Crestline's population was 4,525 at the 2020 census. It is the third largest municipality in Crawford County. The Crawford County portion of Crestline is part of the Bucyrus Micropolitan Statistical Area, while the small portion of the village that extends into Richland County is considered part of the Mansfield Metropolitan Statistical Area. Both sections form the Mansfield–Bucyrus, OH Combined Statistical Area.

Crawford County is a county located in the north central portion of the U.S. state of Ohio. As of the 2020 census, the population was 42,025. Its county seat and largest city is Bucyrus. The county was created in 1820 and later organized in 1836. It was named for Colonel William Crawford, a soldier during the American Revolution. Crawford County comprises the Bucyrus, OH Micropolitan Statistical Area, which is also included in the Mansfield-Ashland-Bucyrus, OH Combined Statistical Area.