GI, Gi or gi may refer to:

• Galvanized iron - iron that has been electrochemically rustproofed with zinc.
• Game Informer - a video games magazine
• Gary, Indiana - a city in Northwest Indiana
• Gastrointestinal - a division of the human anatomy in medicine
• Generic identifier
• Geodætisk Institut - a former Danish cartographic institute
• Geographical indication
• General Instrument - an electronics company
• Gi - the IEEE prefix gibi which represents 2³⁰.
• Gi (Captain Planet character) - a character in the television series Captain Planet and the Planeteers
• (GI) - an album by The Germs
• G.I. - a nickname for a United States Army soldier
• G.I. Joe - a toy soldier series manufactured by Hasbro
• G.I. (comics) - a reference to Genetic Infantryman in the Rogue Trooper fictional universe
• .gi - Gibraltar's country code top-level domain
• Gibraltar
• Gilbert (Gb or Gi) - a former CGS unit of magnetomotive force or magnetic potential
• Gill - a U.S. unit of volume equal to 4 U.S. fluid ounces and an Imperial unit equal to 5 imperial fluid ounces
• Government Issue - a 1980's hardcore band
• Global illumination - the rendering of light in 3D computer graphics scenes
• Global income
• Glycemic index - a ranking system for carbohydrates based on their effect on blood glucose levels
• Graded index
• Grand Island, Nebraska - an American city
• Graph isomorphism problem and the complexity class of problems reducible to it
• Itek Air IATA airline designator
• Keikogi or "Gi" - the clothing worn in judo, karate, and other Japanese martial arts.

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