| Peter O'Brien | |
| Birth Date: | c. 1842 |
| Birth Place: | Dublin, Ireland |
| Death Place: | Chicago, Illinois, United States |
| Placeofburial: | Rosehill Cemetery, Chicago |
| Serviceyears: | 1861–1865 |
| Rank: | Corporal |
| Unit: | Company A, 1st New York Volunteer Cavalry "Lincoln Cavalry" |
| Battles: | Battle of Waynesboro American Civil War |
| Awards: | Medal of Honor |
Peter O'Brien (c. 1842 - September 30, 1898) was an American soldier who fought in the American Civil War. O'Brien received his country's highest award for bravery during combat, the Medal of Honor.[1] O'Brien's medal was won for capturing a Confederate flag, and an officer with his horse and equipment, at the Battle of Waynesboro, Virginia, on March 2, 1865.[1] He was honored with the award on March 26, 1865.[1]
O'Brien was born in Dublin, Ireland. He joined the US Army from New York City in August 1861, and mustered out with his regiment in June 1865.[2] He was later buried in Rosehill Cemetery, Chicago, Illinois.