John Irvin Gregg | |
|---|---|
 Brig. Gen. John I. Gregg | |
| Nickname(s) | Long John |
| Born | July 19, 1826 Bellefonte, Pennsylvania |
| Died | January 6, 1892 (aged 65) Washington, D.C. |
| Place of burial | |
| Allegiance | United States of America Union |
| Service/ | United States Army Union Army |
| Years of service | 1846–1848, 1861–1879 |
| Rank |  Colonel Brevet Major General |
| Commands | 16th Pennsylvania Cavalry Cavalry Corps, Army of the Potomac 8th U.S. Cavalry Regiment |
| Battles/wars | Mexican–American War American Civil War American Indian Wars |
John Irvin Gregg (July 19, 1826 – January 6, 1892) was a career U.S. Army officer. He fought in the Mexican–American War and during the American Civil War as a colonel and near the end of the war as a brevet general in the Union army. In 1866, he was nominated and confirmed as a brevet major general of volunteers and a brevet brigadier general in the Regular Army (United States), both to rank from March 13, 1865.