GT4 or GT-Four may refer to:
Automotive
- SRO GT4, a sports car racing category
- ADAC GT4 Germany, a German-based sports car championship
- Dutch GT4 Championship, a Dutch sports car championship
- GT4 America Series, a North American sports car championship
- GT4 Australia, an Australian sports car championship
- GT4 European Series, a European sports car championship
- Ferrari GT4
- Porsche Cayman GT4
- Porsche 981 Cayman GT4
- Porsche 718 Cayman GT4
- Toyota Celica GT-Four
Other uses
- Gran Turismo 4, a 2004 PlayStation 2 racing video game
- GT4 (tram), a design of articulated tram which has two bogies and two body sections, and specifically:
- GT4 (Bremen), a model of GT4 tram used in the German city of Bremen
- Maschinenfabrik Esslingen GT4, a model of GT4 tram used in Stuttgart and other German cities