Sidney is a city in Shelby County, Ohio, United States, and its county seat. The population was 20,589 at the 2020 census. It is approximately 36 miles (58 km) north of Dayton and 100 miles (160 km) south of Toledo, and is a part of the Dayton metropolitan area. The city is named after English poet Philip Sidney, and many of Sidney'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. In 2009, it was the subject of the documentary film 45365.