A front derailleur chain detachment prevention member is provided that can be easily removed from a front derailleur. The front derailleur chain detachment prevention member is removably mounted on a front derailleur, and has elasticity. The front derailleur chain detachment prevention member is provided with a mounting part, a connecting part, and a regulating part. The mounting part is removably attached to an inner plate of a chain guide. The connecting part extends forward from the mounting part along the inner plate. The regulating part is disposed at a tip of the connecting part, and projects from the inner plate toward an outer plate of the front derailleur.