  We present a 5D axion-neutrino model that explains the Standard Model fermion
mass hierarchy and flavor structure, while simultaneously generating a
high-quality axion. The axion and right-handed neutrinos transform under a 5D
Peccei-Quinn gauge symmetry, and have highly suppressed profiles on the UV
brane where the symmetry is explicitly broken. This setup allows neutrinos to
be either Dirac, or Majorana with hierarchically small sterile neutrino masses.
The axion decay constant originates from the IR scale, which in the
holographically dual 4D description corresponds to the confinement scale of
some new strong dynamics with a high-quality global Peccei-Quinn symmetry that
produces a composite axion and light, composite sterile neutrinos. The sterile
neutrinos could be observed in astrophysical or laboratory experiments, and the
model predicts specific axion--neutrino couplings.
