Cid is a recurring character concept in the Final Fantasy franchise and some of its spin-offs. The Cid that appears in each game is never the same person, nor do the Cids necessarily fill the same role from game to game (although at least three of them have been airship engineers). Some Cids appear as playable characters while others feature in supporting NPC roles. A select few have also appeared as villains and boss encounters. Occasionally, the name of the Cid may also vary, such as Cidolfus Demen Bunansa of Final Fantasy XII.
Though their roles vary, Cids often share similar traits with one another. They tend to be older than the central character, or if not noticeably older at least wiser to the ways of the world. Some Cids such as Cid Pollendina of Final Fantasy IV and Cid Highwind of Final Fantasy VII share an interest in flight and serve as the player's means to an airship. In fact, many Cids share an interest in (or at least become heavily involved with) airships at some point in their respective games.
A Cid also appears in the theatrical film Final Fantasy: The Spirits Within. This Cid, named Dr. Sid, is a scientist voiced by Donald Sutherland. He is the mentor of the film's protagonist, Aki.