  In this note, we discuss the implications of the weak gravity conjecture
(WGC) for general models of large-field inflation with a large number of axions
$N$. We first show that, from the bottom-up perspective, such models admit a
variety of different regimes for the enhancement of the effective axion decay
constant, depending on the amount of alignment and the number of instanton
terms that contribute to the scalar potential. This includes regimes of no
enhancement, power-law enhancement and exponential enhancement with respect to
$N$. As special cases, we recover the Pythagorean enhancement of $N$-flation,
the $N$ and $N^{3/2}$ enhancements derived by Bachlechner, Long and McAllister
and the exponential enhancement by Choi, Kim and Yun. We then analyze which
top-down constraints are put on such models from the requirement of consistency
with quantum gravity. In particular, the WGC appears to imply that the
enhancement of the effective axion decay constant must not grow parametrically
with $N$ for $N \gg 1$. On the other hand, recent works proposed that axions
might be able to violate this bound under certain circumstances. Our general
expression for the enhancement allows us to translate this possibility into a
condition on the number of instantons that couple to the axions. We argue that,
at large $N$, models consistent with quantum gravity must either allow
super-Planckian field excursions or have an enormous, possibly even
exponentially large, number of dominant instanton terms in the scalar
potential.
