| Abbreviation | Definition |
|---|---|
| IBOP | International Brotherhood of Operative Potters |
| IBPAW | International Brotherhood of Pottery and Allied Workers |
| IBPO | International Brotherhood of Police Officers |
| IBT | International Brotherhood of Teamsters |
| IBU | International Boxing Union |
| IBU | Internationale Biathlon Union |
| IBU | Irish Bridge Union |
| ICCC | International Communion of Charismatic Churches |
| ICCU | Idaho Central Credit Union |
| ICDU | Ibusa Community Development Union |
| ICEU | Inter Company Employees Union |
| ICFTU | International Confederation of Free Trade Unions |
| ICGU | Intimate Care Giving Union |
| ICSF | International Collective in Support of Fishworkers |
| ICTU | Irish Congress of Trade Unions |
| ICU | Industrial Credit Union |
| ICU | International Chalu Union |
| ICU | International Cheer Union |
| ICUF | Iowa Credit Union Foundation |
| ICWU | Industrial and Commercial Workers Union |