IAB may refer to:
Organisations
- Institute of Architects Bangladesh, a professional organisation for architects in Bangladesh
- Interactive Advertising Bureau, for the online advertising industry
- Internal Affairs Bureau, part of the New York City Police Department, US
- International Agrarian Bureau or Green International, based in Prague, Czech Republic
- Institute of Accountants and Bookkeepers, UK
- International Association of Bryologists, promoting bryology (the study of mosses, liverworts, and hornworts)
- Internet Advertising Bureau, a UK trade association
- Internet Architecture Board, a committee of the Internet Engineering Task Force (IETF)
- Islami Andolan Bangladesh, political party in Bangladesh
- Israel Association of Baseball, to promote and develop baseball in Israel
Air force bases
- Isa Air Base, Bahrain
- McConnell Air Force Base (IATA airport code), Wichita, Kansas, US
Science and technology
- IAB meteorite, a group of iron meteorites
- Individual Address Block, in computer networking
Other uses
- International Accounting Bulletin, a UK accountancy publication