| Abbreviation | Definition |
|---|---|
| IRAA | Investors Rights Association of America |
| IRCA | International Ragdoll Cats Association |
| IRCA | International Railway Congress Association |
| IRMA | Information Resources Management Association |
| IRRA | Industrial Relations Research Association |
| IRRDB | International Rubber Research and Development Board |
| IRTA | International Reciprocal Trade Association |
| IRTA | Irish Rider Training Association |
| IRTE | Institute of Road Transport Engineers |
| ISA | Instrumentation Society of America |
| ISA | International Society of Appraisers |
| ISA | International Society of Arboriculture |
| ISA | International Society of Automation |
| ISA | International Sociological Association |
| ISA | Irish Software Association |
| ISACA | Information Systems Audit And Control Association |
| ISAKMP | Interenet Security Association Key Management Protocol |
| ISAKMP | Internet Security Association Key Management Protocol |
| ISAKMP | The Internet Security Association And Key Management Protocol |
| ISAP | International Society for Applied Phycology |