| Abbreviation | Definition |
|---|---|
| IFRP | International Fair of Racing Pigeons |
| IGL | intracellular growth locus |
| IIRA | International Ice Racing Association |
| IJR | Ian Johns Racing |
| IKR | Indoor Kart Racing |
| IMBRA | International Model Boat Racing Association |
| IMRA | Illinois Midget Racing Association |
| IMRA | International Mile Racing Association |
| IMRC | International Motorcycle Race Cup |
| INFG | If Not For Grace |
| IORF | International Obstacle Racing Federation |
| IRA | Interstate Racing Association |
| IRA | Irish Racing Association |
| IRD | Interloc Racing Design |
| IRGP | Inside Racing Grand Prix |
| IRL | Indy Racing League |
| IRL | Insane Racing League |
| IRL | International Racing League |
| IROC | Idiot Racer On Crack |
| IROC | Interleague Racing Online Competition |