| Abbreviation | Definition |
|---|---|
| IRSA | Indiana Recreational Sports Association |
| ISA | Iowa Soccer Association |
| ISAC | International Schools Athletic Conference |
| ISAF | International Sailing Federation |
| ISB | Illegal Soap Box |
| ISB | International Sports Broadcasting |
| ISBA | International Short Break Association |
| ISBA | International Stable Breeder's Association |
| ISBC | International Short Break Conference |
| ISBF | Illegal Soap Box Federation |
| ISBF | International Sogo Budo Federation |
| ISBG | In Shape Big Guys |
| ISBG | Inter-Stat Board Games |
| ISBL | International Simulated Baseball League |
| ISBS | International Society of Biomechanics in Sports |
| ISBT | International Student Badminton Tournament |
| ISC | Individual Scrum Championship |
| ISC | Interactive Strength Challenger |
| ISC | Irish Sports Council |
| ISCA | Indoor Soccer Coaches Association |