New Carlisle is a city in Bethel Township, Clark County, Ohio, United States. The population was 5,559 at the 2020 census. It is part of the Springfield, Ohio Metropolitan Statistical Area. New Carlisle was originally called Monroe, and under the latter name was laid out in 1810. The present name is a transfer from Carlisle, Pennsylvania, the birthplace of some of the first settlers. A post office called New Carlisle has been in operation since 1828. New Carlisle was incorporated as a village in 1831.