| Harry J. O'Brien | |
| Birth Date: | 31 October 1884 |
| Birth Place: | New Haven, Connecticut, U.S. |
| Death Place: | Philadelphia, Pennsylvania, U.S. |
| Player Sport1: | Football |
| Player Years2: | c. 1907–1909 |
| Player Team2: | Swarthmore |
| Player Positions: | Quarterback |
| Coach Sport1: | Football |
| Coach Years2: | 1914–1915 |
| Coach Team2: | Gettysburg |
| Coach Years3: | 1916–1918 |
| Coach Team3: | The Citadel |
| Coach Years4: | 1920–1921 |
| Coach Team4: | The Citadel |
| Coach Years5: | 1922–1925 |
| Coach Team5: | Drexel |
| Coach Sport6: | Basketball |
| Coach Years7: | 1914–1916 |
| Coach Team7: | Gettysburg |
| Coach Years8: | 1916–1918 |
| Coach Team8: | The Citadel |
| Coach Years9: | 1922–1925 |
| Coach Team9: | Drexel |
| Coach Sport10: | Baseball |
| Coach Years11: | 1917–1918 |
| Coach Team11: | The Citadel |
| Overall Record: | 25–51–6 (football) 42–37 (basketball) 3–9 (baseball) |
Harry Joseph O'Brien (October 31, 1884 – August 23, 1955),[1] [2] nicknamed "Shorty", was an American football, basketball, and baseball coach. He was the fifth head football coach at The Citadel, serving for five seasons, from 1916 to 1918 and from 1920 to 1921, compiling a record of 14–15–4.[3] O'Brien also coached basketball and baseball for The Citadel for two seasons during World War I. He tallied a record of 6–2 in basketball and 3–9 in baseball.[4] O'Brien died of coronary thrombosis on August 23, 1955, at his home in Philadelphia.[5] [6]