  High-energy collisions at the High-Luminosity Large Hadron Collider (HL-LHC)
will produce an enormous flux of particles along the beam collision axis that
is not accessible by existing LHC experiments. Multi-particle production in the
far-forward region is of particular interest for astroparticle physics.
High-energy cosmic rays produce large particle cascades in the atmosphere,
extensive air showers (EAS), which are driven by hadron-ion collisions under
low momentum transfer in the non-perturbative regime of QCD. Thus, the
understanding of high-energy hadronic interactions in the forward region is
crucial for the interpretation of EAS data and for the estimation of
backgrounds for searches of astrophysical neutrinos. The Forward Physics
Facility (FPF) is a proposal to build a new underground cavern at the HL-LHC
which will host a variety of far-forward experiments to detect particles
outside the acceptance of the existing LHC experiments.
  We will present the current status of plans for the FPF and highlight the
synergies with astroparticle physics. In particular, we will discuss how
measurements at the FPF will improve the modeling of high-energy hadronic
interactions in the atmosphere and thereby reduce the associated uncertainties
of measurements in the context of multi-messenger astrophysics.
