| IAU | International Astronomical Union |
|---|---|
| IBU | International Biathlon Union (skr.) |
| IBU | International Boxing Union (skr.) |
| IRU | International Road Transport Union (skr.), Medzinárodná cestná unia (angl.skr.) |
| IUC | International Union of Chemistry |
| NU | National Union |
| NUC | National Union Catalog (skr.) |
| UIC | Union Internationale des Chemins de Fer (skr.), Medzinárodná únia železníc (franc.skr.) |
| UIDA | Union Internationale des Arts (skr.) |
| UIS | Union Internationale de Secours (skr.) |