GTI may refer to:
Automotive
- Grand Tourer Injection, a car model variant
- Maserati 3500 GTI, the first GTI car ever, from 1961
- Volkswagen Golf GTI, a famous hot hatch
- Peugeot 205 GTI, a famous hot hatch
- Suzuki Swift GTi, Suzuki GTi variant
- GTi Engineering, an auto racing team
Other uses
- Galway Technical Institute
- Global Tiger Initiative, a conservation effort funded in part by the World Bank
- Global Terrorism Index
- GrafTech, a graphite manufacturing company, NYSE symbol GTI
- Grid-tie inverter, an apparatus to convert DC electrical (solar, wind) energy to AC and deliver it back to the grid
- GT Interactive, a video game publisher and distributor
- Guilford Transportation Industries, a transportation company
- Atlas Air, ICAO code GTI
- Pokémon Mystery Dungeon: Gates to Infinity, a game in the Pokémon Mystery Dungeon series
