  An overview of the multi-messenger capabilities of the Pierre Auger
Observatory is presented. The techniques and performance of searching for
Ultra-High Energy neutrinos, photons and neutrons are described. Some of the
most relevant results are reviewed, such as stringent upper bounds that were
placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on
neutrinos emitted from compact binary mergers that were detected by LIGO and
Virgo during their first and second observing runs, as well as searches for
high energy photons and neutrons from the Galactic center that constrain the
properties of the putative Galactic PeVatron, observed by the H.E.S.S.\
collaboration. The observation of directional correlations between ultra-high
energy cosmic rays and either high energy astrophysical neutrinos or specific
source populations, weighted by their electromagnetic radiation, are also
discussed. They constitute additional multi-messenger approaches aimed at
identifying the sources of high energy cosmic rays.
