ISG
- ISG Business School
- ISG Ltd
- Idaho State Guard
- Immunoglobulin therapy
- Independent Senators Group
- Indian School, Al-Ghubra
- Information Security Group
- Interferon-stimulated gene
- International School Groningen
- International School in Genoa
- International School of Geneva
- International Socialist Group
- International Steel Group
- Interserve
- Iowa State Guard
- Iraq Study Group
- Iraq Survey Group
- Irish Sign Language
- Islamic Solidarity Games
- New Ishigaki Airport