| 21st Ohio Infantry Regiment | |
|---|---|
 Ohio state flag | |
| Active | April 1861– July 1865 |
| Country | United States of America |
| Allegiance | Union |
| Branch | Infantry |
| Type | Regiment |
| Engagements | Battle of Scary Creek Battle of Ivy Mountain Stones River Chickamauga Atlanta Campaign Sherman's March to the Sea Carolinas Campaign Bentonville |
The 21st Ohio Infantry Regiment was an infantry regiment in the Union Army during the American Civil War. Mostly an all-volunteer unit, with the exception of a few draftees, the 21st Ohio served for both ninety-day and three-year enlistments and fought exclusively in the Western Theater. It saw action in some of the war's bloodiest battles including Stones River, Chickamauga, the Atlanta Campaign, and Sherman's March to the Sea.