| Abbreviation | Definition |
|---|---|
| IRPA | International Relations Politics Association |
| IRPC | Institute for Religion Politics and Culture |
| IRSP | Irish Republican Socialist Party |
| IS | Independent Sector |
| ISCAP | Institute for the Study of Citizens and Politics |
| ISDCI | International Solidarity for Democratic Change in |
| ISI | Import Substitution Industrialization |
| ISIL | International Society for Individual Liberty |
| ISIL | Islamic State of Iraq and Levant |
| ISIS | International countries of Iran and Siberia |
| ISIS | Islamic State in Iraq and al-Shām |
| ISIS | Islamic State in Iraq and al-Shm |
| ISKP | Islamic State Khorasan Province |
| ISNA | Intersex Society of North America |
| ISO | International Socialist Organization |
| ISRP | Irish Socialist Republican Party |
| ITAK | Illankai Tamil Arasu Kachchi ( Sri Lanka) |
| ITAR | International Traffic in Arms Regulation |
| ITC | International Terrorist Coalition |
| ITK | Inuit Tapiriit Kanatami |