ISG may refer to:
- Insight Sourcing Group, a management consulting firm focused exclusively on Strategic Sourcing, Spend Analytics, and Procurement Process Transformation.
- Impartion et Service de Gestion, an IT business founded in 2007 in Montreal, Canada
- International School of Geneva, the oldest international school in the world
- International School Groningen an international school in Groningen, current programme of the school is IBMYP
- Indian School Al Ghubra, a K-12 school in Muscat, Oman
- Information Security Group, ISG is one of the largest academic security groups in the world
- Institut supérieur de gestion, a renowned business school in Paris, France.
- Integrated Starter-Generator, Part of an automotive Start-stop_system
- Interactive Storytelling Game, a type of role-playing game
- International Socialist Group, a Trotskyist group and British section of the Fourth International between 1987 and 2009
- International Steel Group, a steel company headquartered in Cleveland, Ohio.
- International Support Group, a non-profit professional association registered in the Netherlands
- Interactive Support Group, a defunct CD-I development company
- Iraq Study Group, a 2006 Congressionally appointed panel charged with assessing the situation in Iraq, also known as the Baker-Hamilton Commission
- Iraq Survey Group, the 2003-2005 investigative mission in the Iraqi WMD search program that produced the Duelfer Report
- International School of Gemology, an internet based hobby group, has inservices for insurance agents to fill in forms correctly.
- IATA airport code for Ishigaki Airport on Ishigaki Island, Okinawa, Japan
- Intelligent Service Gateway, a technology from Cisco Systems, to manage subscribers in Broadband, Wireline & Wireless deployments
- Interferon-stimulated genes, a varied group of genes that are switched on by interferon to tackle viral infection.