  The high temperature and electron degeneracy attained during a supernova
allow for the formation of a large muon abundance within the core of the
resulting proto-neutron star. If new pseudoscalar degrees of freedom have large
couplings to the muon, they can be produced by this muon abundance and
contribute to the cooling of the star. By generating the largest collection of
supernova simulations with muons to date, we show that observations of the
cooling rate of SN 1987A place strong constraints on the coupling of axion-like
particles to muons, limiting the coupling to $g_{a\mu} <
10^{-7.5}~\text{GeV}^{-1}$.
