 0000 American Physical Society 0000 American Physical Society In a number of widely studied materials, such as Si, AlAs, Bi, graphene, MoS 0 , and many transition metal dichalcogenide monolayers, electrons acquire an additional, spinlike degree of freedom at the degenerate conduction band minima, also known as "valleys." External symmetry-breaking fields such as mechanical strain, or electric or magnetic fields, can tune the valley polarization of these materials, making them suitable candidates for "valleytronics." Here we study a quantum well of AlAs, where the two-dimensional electrons reside in two energetically degenerate valleys. By fabricating a strain-inducing grating on the sample surface, we engineer a spatial modulation of the electron population in different valleys, i.e., a "valley superlattice" in the quantum well plane. Our results establish a novel manipulation technique of the valley degree of freedom, paving the way to realizing a valley-selective layered structure in multivalley materials, with potential application in valleytronics. National Science Foundation 00.00000/000000000 ECCS 0000000 DMR 0000000 MRSEC DMR 0000000 Gordon and Betty Moore Foundation 00.00000/000000000 GBMF0000 U.S. Department of Energy 00.00000/000000000 DEFG00-00-ER00000 marker L_SUGG With the ubiquitous, Si-based electronics approaching their fundamental physical limitations, there is an active push to explore novel device concepts. An emergent field is "valleytronics" which harnesses electrons