The crumpling of two-dimensional (2D) materials is one of the most widely used ways to create three-dimensional (3D) out-of-plane structures from 2D materials and to apply in-plane strain for strain-induced material property modulation. Although the elastic compressive strain induced crumpling of 2D materials is a simple and versatile way to form 3D structures, the resulting structures are rather simple where crumples are formed in a delocalized manner. Here, we report a new approach inspired by crack lithography to localize deformation and achieve localized crumpling of 2D materials. As a result, a mixed-dimensional structure composed of flat (2D) and crumpled (3D) structure is formed monolithically in 2D materials. We present structural analysis of our mixed-dimensional structure of graphene, where the localized prestrain was amplified to be 330% of the macroscale prestrain. In addition, we demonstrate the material densification and the strain localizations of our mixed-dimensional structure of monolayer MoS 2 and graphene based on Raman and photoluminescence spectral characterizations. Finally, our mixed-dimensional graphene structure is fabricated into a stretchable strain sensor, where it exhibits four times enhanced gauge factor compared to that of delocalized crumpled graphene.