Sidney is a city in and the county seat of Shelby County, Ohio, United States, located approximately 36 miles north of Dayton and 100 miles south of Toledo. The population was 20,421 at the time of the 2020 census. It is named after English poet Philip Sidney, and many of the city's elementary schools are named after famous writers, including Ralph Waldo Emerson, Henry Wadsworth Longfellow, and John Greenleaf Whittier. Sidney was the recipient of the 1964 All-America City Award.