| Abbreviation | Definition |
|---|---|
| NICAS | National Indoor Climbing Achievement Scheme |
| NICAS | National Indoor Climbing Award Scheme |
| NIJF | Northern Ireland Judo Federation |
| NIKB | Northern Ireland Karate Board |
| NIL | Zero |
| NIM | Non-Integrated Moves |
| NIPOGA | Nigerian Polytechnic Games |
| NIQ | No Item Quake |
| NIRA | National Import Racing Association |
| NIRA | National In-line Racing Association |
| NIRA | National Intercollegiate Rodeo Association |
| NIRSA | National Intramural Recreational Sports Association |
| NIRSA | National Intramural-Recreational Sports Association |
| NISS | New Injury Severity Score |
| NISS | Niseko International Snowsports School |
| NIT | National Invitational Tournament |
| NIT | Not In Tournament |
| NITP | National Intensive Training Program (Basketball South Australia) |
| NITSA | Northern Ireland Target Sports Association |
| NJA | National Jousting Association |