Jack may refer to:
- The character from Final Fantasy VIII.
- The character from Final Fantasy IX.
- Jaggedy-Eared Jack, a Notorious Monster from Final Fantasy XI.
- Lumber Jack, a Notorious Monster from Final Fantasy XI.
- The character from King's Knight -Wrath of the Dark Dragon-.
- The character from Final Fantasy Type-0.
- The character from Final Fantasy Crystal Chronicles.
- The character from Chocobo Racing.
- Spencer's name in the Japanese release of Final Fantasy Mystic Quest.
Jack is a male given name and sometimes as a surname. In English it is traditionally used as the diminutive form of the name John, though it is also often given as a proper name in its own right.
The name Jack is unique in the English language for the frequency of its use as a verb and a noun for many common objects and actions; and also its use in many compound words and phrases: jack-of-all-trades, jackknife, jackpot, jack tar, hijack, union jack, jack straw (scarecrow), apple jack, lumberjack, jackhammer, jackdaw, jack o'lantern, jack-off, jack-in-the-box, jack of clubs (playing cards), etc. The varied uses are traceable to the common use of the word as a by-name of a man.