  Models of large-field inflation based on axion-like fields with shift
symmetries can be simple and natural, and make a promising prediction of
detectable primordial gravitational waves. The Weak Gravity Conjecture is known
to constrain the simplest case in which a single compact axion descends from a
gauge field in an extra dimension. We argue that the Weak Gravity Conjecture
also constrains a variety of theories of multiple compact axions including
N-flation and some alignment models. We show that other alignment models entail
surprising consequences for how the mass spectrum of the theory varies across
the axion moduli space, and hence can be excluded if further conjectures hold.
In every case that we consider, plausible assumptions lead to field ranges that
cannot be parametrically larger than the Planck scale. Our results are strongly
suggestive of a general inconsistency in models of large-field inflation based
on compact axions, and possibly of a more general principle forbidding
super-Planckian field ranges.
