  We provide a derivation from first principles of the primordial bispectrum of
scalar perturbations produced during inflation driven by a canonically
normalized scalar field whose potential exhibits small sinusoidal modulations.
A potential of this type has been derived in a class of string theory models of
inflation based on axion monodromy. We use this model as a concrete example,
but we present our derivations and results for a general slow-roll potential
with superimposed modulations. We show analytically that a resonance between
the oscillations of the background and the oscillations of the fluctuations is
responsible for the production of an observably large non-Gaussian signal. We
provide an explicit expression for the shape of this resonant non-Gaussianity.
We show that there is essentially no overlap between this shape and the local,
equilateral, and orthogonal shapes, and we stress that resonant non-Gaussianity
is not captured by the simplest version of the effective field theory of
inflation. We hope our analytic expression will be useful to further
observationally constrain this class of models.
