  We examine scenarios in which a dark sector (dark matter, dark radiation, or
dark energy) couples to the active neutrinos. For light and weakly-coupled
exotic sectors we find that scalar, vector, or tensor dark backgrounds may
appreciably impact neutrino propagation while remaining practically invisible
to all other phenomenological probes. The dark medium may induce small
departures from the Standard Model predictions or even offer an alternative
explanation of neutrino oscillations. While the propagation of neutrinos is
affected in all experiments, atmospheric data currently represent the most
promising probe of the new physics scale. We quantify the future sensitivity of
the ORCA detector of KM3NeT and the IceCube experiment and find that all exotic
effects can be constrained at the level of a few percent of the Earth matter
potential, with couplings mediating $\mu$-neutrino transitions being most
constrained. Long baseline experiments like DUNE may provide additional
complementary information on the scale of the dark sector.
