| Abbreviation | Definition |
|---|---|
| IRIS | Inter-Religiousraat In Suriname |
| IRK | Islamic Religious Knowledge |
| IRM | Iskcon Revival Movement |
| IRO | Inter-Religious Organization |
| IROC | In Rememberance Of Christ |
| IRTC | Institute for Religion, Technology, and Culture |
| IRW | Iberian Religious World |
| IS | Islamic State |
| IS | Islamic Studies |
| ISA | In Shaa Allah (at Allah's will) |
| ISA | Independent Spiritualist Association |
| ISARC | Interfaith Social Assistance Reform Coalition |
| ISBC | Indian Springs Baptist Church |
| ISBE | International Standard Bible Encyclopedia |
| ISBL | International Society of Biblical Literature |
| ISBO | Islamic States Boarding Organisation |
| ISCF | Inter School Christian Fellowship |
| ISDB | Islamic Development Bank |
| ISDCL | International Society for the study of Deuterocanonical and Cognate Literature |
| ISG | Innocent Sinners Guild |