| Abbreviation | Definition |
|---|---|
| UBEC | Union of Banana Exporting Countries |
| UBPL | Upper Bound Poverty Line |
| UCAF | United Countries Air Force |
| UE | United Europe |
| UG | Uganda |
| UGA | Uganda |
| UK | United Kingdom |
| UK-EWNI | United Kingdom - England, Wales, and Northern Ireland |
| UKR | Ukraine |
| UM | USA Minor Outlying Islands |
| UNCCD | United Nations Convention to Combat Desertification |
| UNIDO | United Nations Industrial Development Organisation |
| UNWTO | United Nations World Tourism Organisation |
| UP | Upper Peninsula |
| URS | Union of Soviet Socialist Republics |
| US | United States |
| US | United States |
| US? | United States |
| US€ | United States |
| USSR | Union of Soviet Socialist Republics |