Over the past decade, multi-messenger astronomy has become a unique field that offers
insights into the high-energy Universe by integrating data from a variety of cosmic
messengers. This field is about to advance significantly with the deployment of next-
generation neutrino telescopes, such as those currently being built in the Mediterranean Sea
by the KM3NeT Collaboration. KM3NeT (Cubic Kilometre Neutrino Telescope) is a research
infrastructure housing undersea Cherenkov neutrino telescopes, with two sites: ARCA and
ORCA. KM3NeT/ORCA, situated off the French coast, is designed to detect neutrinos with
energies in the GeV–TeV range and focuses on particle physics. It is currently operational
with 24 instrumented detection units. KM3NeT/ARCA, located offshore of Sicily, aims to
detect astrophysical neutrinos across a broad range of energies, from 100 GeV up to multi-
PeV, and will play a major role in advancing multi-messenger astronomy. With 33 deployed
detection units, KM3NeT/ARCA is already yielding promising physics results. This
contribution introduces neutrino astronomy, highlights the progress at both KM3NeT sites,
and explains how this project will improve our understanding of cosmic sources through
neutrino detection.