ISG may refer to:
Academics Information Security Group, academic information security group in Royal Holloway, University of London Indian School, Al-Ghubra, a K-12 school in Muscat, Oman International School of Geneva, an international school in Geneva, Switzerland International School in Genoa, an international school in Genoa, Italy International School Groningen, an international school in Haren, Netherlands ISG Business School, a business school in Paris, France
Organisations Idaho State Guard, active during World War II Independent Senators Group, a Canadian Senate parliamentary group Interactive Support Group, a defunct CD-I development company International Steel Group, a steel company headquartered in Cleveland, Ohio Interserve Group, a UK construction company Iowa State Guard, active during World War II ISG Ltd, a UK construction company
Transportation Integrated Starter-Generator, part of an automotive start-stop system New Ishigaki Airport (IATA airport code) on Ishigaki Island, Okinawa, Japan
Other uses In situ gasification, a process in underground coal gasification (UCG) Instruction Stream Generator, also called random test generator Interferon-stimulated genes, a varied group of genes that are switched on by interferon to tackle viral infection International Socialist Group, a Trotskyist group and British section of the Fourth International between 1987 and 2009 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 Irish Sign Language (ISO 639 code isg) Islamic Solidarity Games, multinational multi-sport event Immune serum globulin