| Abbreviation | Definition |
|---|---|
| UGF | United Giver’s Fund |
| UGF | United Givers Fund |
| UGN | United Grassroots Network |
| UHMS | Undersea & Hyperbaric Medicine Society |
| UHO | United Health Organization |
| UHO | United Homeless Organization |
| UIB | Upshaw Institute for the Blind |
| UIM | United Indian Missions, Inc. |
| UJA | United Jewish Appeal |
| UJC | United Jewish Communities |
| UJCI | United Jewish Communities, Inc. |
| UJF | United Jewish Federation |
| UJFGP | United Jewish Federation of Greater Pittsburgh |
| UJO | United Jewish Organizations |
| UJP | United for Justice with Peace |
| UKAID | United Kingdom Aid |
| UKLA | United Kingdom Law Associates |
| UKSG | United Kingdom Serials Group |
| UL | Underwriters Laboratories |
| ULF | United Leukodystrophy Foundation |