Sidney is a city in Shelby County, Ohio, United States. The population was 20,211 at the 2000 census. It is named after English poet Sir Phillip Sidney and is the county seat of Shelby County.
Sidney was the recipient of the 1964 All-America City Award. In 2009, it was the subject of the documentary film 45365.
Sidney features some unusual architecture for a small town, including the 1881 Second Empire courthouse, the 1877 Gothic revival Monumental Building, dedicated to the county's Civil War dead, the 1918 early-modern People's Federal Savings and Loan Association was designed by Louis Sullivan, a National Historic Landmark, and the "smallest house in Sidney" on Shelby Street.