Camp Dennison is an unincorporated community 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. During the American Civil War, Camp Dennison served as a military recruiting and training post for the United States Army. It is named for William Dennison, the 24 Governor of Ohio and U.S. Postmaster General under President Abraham Lincoln.