GRB or Grb may refer to
- Austin Straubel International Airport (IATA airport code), an airport southwest of Green Bay, Wisconsin, U.S.
- Gamma-ray burst, a type of very violent cosmic event, detectable on Earth as a short, intense burst of gamma rays.
- Game Rating Board, a South Korean game rating organization.
- A word in the Croatian for the Coat of arms of Croatia, Hrvatski Grb.
- Grebo language (ISO 639-2 language code), spoken by the Grebo people of Liberia and the Krumen of Ivory Coast.