| Abbreviation | Definition |
|---|---|
| IMPACT | Intense Motivated Performance Altering Conditioning Techniques |
| IMS | Indianapolis Motor Speedway |
| IMSAC | Indian Motor Sports Appeal Court |
| IMSN | Inter Mountain Sports Network |
| IMWT | In Moyes We Trust |
| IMYTA | I Match Your Trick Association |
| INBF | International Natural Bodybuilding and Fitness |
| INF | International Netball Federation |
| INRC | Indian National Rally Championship |
| INSC | Irish National Sailing Club |
| INT | Interception |
| IOA | Independent Olympic Athlete |
| IOC | International Othello Competitors |
| IOCA | Intercollegiate Outing Club Association |
| IOCA | International Optimist Class Association (sailing) |
| IOCJ | International Order of Camel Jockeys |
| IOCL | International Online Competition League |
| IOCN | International Olympic Committee News |
| IOCW | Isle Of Capri Waterloo |
| IOD | International One Design |