GTI may refer to:

  • Volkswagen Golf GTI, a car
  • GTi Engineering, an auto racing team
  • Galway Technical Institute
  • Grand Tourer Injection, a car model variant
  • GT Interactive, a video game publisher and distributor
  • Guilford Transportation Industries, a transportation company
  • GrafTech, a graphite manufacturing company, NYSE symbol GTI
  • Atlas Air, ICAO code GTI
  • Grid-tie_inverter, an aparatus to convert dc electrical (solar, wind) energy to ac and deliver it back to the grid.