  We use the Trans-Planckian Censorship Conjecture (TCC) to constrain the decay
constants $f$ characterizing a set of N identical axion-like fields with cosine
potentials, improving upon the precision of other Swampland conjectures and
existing string-theoretic arguments. We find that consistency with the TCC
requires any such set of axion-like fields to satisfy $f\sqrt{N} \lesssim
0.6M_{pl}$, where $M_{pl}$ is the reduced Planck mass. We show that this bound
makes models of axion-driven inflation incapable of simultaneously producing
the required number of e-foldings and the observed scalar spectral tilt. In
contrast, we find that models of axion quintessence can be simultaneously
compatible with the TCC and observational data, provided that the axions'
initial field values are set near the maxima of their potentials to within
roughly $\pm \frac{\pi}{5}f$.
