Camp Dennison is a census-designated place (CDP) just outside Indian Hill in southern Symmes Township, Hamilton County, Ohio, United States. Although it is unincorporated, it has a post office, with the ZIP code of 45111. The population was 375 at the 2010 census. During the American Civil War, Camp Dennison served as a military recruiting and training post for the United States Army (see Camp Dennison). It is named for William Dennison, the 24th Governor of Ohio and U.S. Postmaster General under President Abraham Lincoln.