| Abbreviation | Definition |
|---|---|
| NRG | Next Racing Generation |
| NRRS | National Road Racing Series |
| NRT | No Reportable Trace |
| NSSR | National Straightline Snowmobile Racing |
| NTPA | Natchez Trace Parkway Association |
| NTR | Nightly Talladega Racing |
| NTRA | National Thoroughbred Racing Association |
| NTSR | North Texas Street Racing |
| NURP | National Union of Racing Pigeons |
| NWRA | North West Racing Association |
| NYRA | New York Racing Association |
| NZRB | New Zealand Racing Board |
| OARA | Odyssey Adventure Racing Academy |
| OATS | Outside Agencies Tracing Service |
| OBC | Outboard Boating Club |
| OBR | Ole Buhl Racing |
| OBRA | Oregon Barrel Racing Association |
| OBRA | Oregon Bicycle Racing Association |
| OBUS | Orthopedic Brace Upright Support |
| OCIR | Orange County International Raceway |