GCI is the extension given to files used by the older version of the popular video game Grand Theft Auto 2. GCI is a game data file that was stored in the " Data " folder. A file named " nyc.gci " was used to modify the game from standard gameplay. Such an operation consisted in replacing the original file with the file in which the changes were made.

A tool called GTA 2 File Editor was used to edit GCI files.