Zack Fair is a non-player character from Final Fantasy VII and the main protagonist of its prequel, Crisis Core -Final Fantasy VII-. The wielder of the Buster Sword before Cloud, Zack is a 1st Class SOLDIER and is Cloud's best friend during their time working for Shinra. However, after Sephiroth goes insane, they become test subjects to Professor Hojo, and Zack ultimately sacrifices himself to save Cloud's life. He is also Aerith Gainsborough's former boyfriend. He is affectionately nicknamed "the puppy" in Before Crisis and Crisis Core.
In Final Fantasy VII, Zack only appears in flashback sequences, which portray him as almost identical to Cloud Strife, the game's main protagonist, in physical appearance except having black hair, which is longer than Cloud's. When strung together, the sequences explain a great deal about Cloud's past and his connection to Sephiroth, the game's arch-villain. In Crisis Core, Zack's backstory and role in Cloud's pasts are greatly expanded upon. Zack also appears in Last Order -Final Fantasy VII-, Before Crisis -Final Fantasy VII-, and in Final Fantasy VII: Advent Children.