A foldable display device assembly includes a rigid film having first and second sections spaced apart from each other, the rigid film being foldable about a folding axis disposed between the first and second sections of the rigid film; an adhesion structure having first and second adhesion sections spaced apart from each other, the first and second adhesion sections being disposed on the first and second sections of the rigid film, respectively; a lower flexible module disposed on the adhesion structure; a flexible display module disposed on the lower flexible module; and an upper flexible module disposed on the flexible display module.