  Moir\'e superlattices of two-dimensional van der Waals materials have emerged
as a powerful platform for designing electronic band structures and discovering
emergent physical phenomena. A key concept involves the creation of
long-wavelength periodic potential and moir\'e bands in a crystal through
interlayer hybridization when two materials are overlaid. Here we demonstrate a
new approach based on spatially periodic dielectric screening to create moir\'e
bands in a monolayer semiconductor. It relies on reduced dielectric screening
of the Coulomb interactions in monolayer semiconductors and their environmental
dielectric-dependent electronic band structure. We observe optical transitions
between moir\'e bands in monolayer WSe$_{2}$ when it is placed close to small
angle-misaligned graphene on hexagonal boron nitride. The moir\'e bands are a
result of long-range Coulomb interactions, strongly gate-tunable, and can have
versatile superlattice symmetries independent of the crystal lattice of the
host material. Our result also demonstrates that monolayer semiconductors are
sensitive local dielectric sensors.
