A movable headrest includes a base member including a headrest stay; a movable member that is slidable relative to the headrest stay; and a lock mechanism that locks the movable member such that the movable member is restrained from sliding relative to the headrest stay. The movable member includes a flexure part that bends due to a load received from a head of an occupant, a frame part that supports the flexure part, and an engaging portion. The frame part includes a sliding portion that slides relative to the headrest stay, and when the flexure part is bent such that the engaging portion is moved relative to the frame part, the movable member is unlocked.