| 100th Regiment Pennsylvania Volunteer Infantry | |
|---|---|
 | |
| Active | August 31, 1861 to July 24, 1865 |
| Country | United States |
| Allegiance | Union |
| Branch | Infantry |
| Size | 2,014 |
| Engagements | Battle of Secessionville Second Battle of Bull Run Battle of Chantilly Battle of South Mountain Battle of Antietam Battle of Fredericksburg Siege of Vicksburg Siege of Jackson Knoxville Campaign Rapidan Campaign Battle of the Wilderness Battle of Spotsylvania Court House Battle of North Anna Battle of Totopotomoy Creek Battle of Cold Harbor Siege of Petersburg Battle of the Crater Battle of Globe Tavern Battle of Boydton Plank Road Battle of Fort Stedman Appomattox Campaign Third Battle of Petersburg |
The 100th Regiment Pennsylvania Volunteer Infantry ("The Roundheads" and "The Round Head Regiment") was an infantry regiment that served in the Union Army during the American Civil War.