| Abbreviation | Definition |
|---|---|
| NVV | Nederlands Verbond van Vakverenigingen |
| NWCP | Negotiated Workers' Compensation Program |
| NWFU | North West Football Union |
| NWLB | National Workers Labor Board |
| NWQU | North Wales Quarrymen's Union |
| NWTTA | Northwest Territories Teachers' Association (Canada) |
| NWU | National Workers Union |
| NWU | National Writers Union |
| NWU | Nordic Walking Union |
| NYSNA | New York State Nurses Association |
| NYSUT | New York State United Teachers |
| OANIU | Onitsha Ado National Improvement Union |
| OAPU | Otan Ayegbaju Progressive Union |
| OATU | Outside And Against The Unions |
| OAU | Organisation of American Union |
| OAU | Organization Of American Unity |
| OCCU | Oakland County Credit Union |
| OCCU | Oklahoma Central Credit Union |
| OCCU | Orange County Credit Union |
| OCLU | Ohio Civil Liberties Union |