| U | University |
| UCLA | U of California at Los Angeles |
| unc | uncle |
| UNESCO | United Nations Educational, Scientific and Cultural Organization |
| UNO | United Nations Organization |
| USAAC | United States Army Air Corps |
| USAAF | United States Army Air Force |
| USAF | United States Air Force |
| USARC | United States Army Recruiting Command |
| USN | United States Navy |
| USNR | United States Naval Reserve |
| Utd | United |