  The sources and fluxes of superGZK neutrinos, $E>10^{20}$ eV, are discussed.
The fluxes of {\em cosmogenic neutrinos}, i.e. those produced by ultra-high
energy cosmic rays (UHECR) interacting with CMB photons, are calculated in the
models, which give the good fit to the observed flux of UHECR. The best fit
given in no-evolutionary model with maximum acceleration energy $E_{\rm
max}=1\times 10^{21}$ eV results in very low flux of superGZK neutrinos an
order of magnitude lower than the observed flux of UHECR. The predicted
neutrino flux becomes larger and observable by next generation detectors at
energies $10^{20} - 10^{21}$ eV in the evolutionary models with $E_{\rm
max}=1\times 10^{23}$ eV. The largest cosmogenic neutrino flux is given in
models with very flat generation spectrum, e.g. $\propto E^{-2}$. The neutrino
energies are naturally high in the models of {\em superheavy dark matter and
topological defects}. Their fluxes can also be higher than those of cosmogenic
neutrinos. The largest fluxes are given by {\em mirror neutrinos}, oscillating
into ordinary neutrinos. Their fluxes obey some theoretical upper limit which
is very weak, and in practice these fluxes are most efficiently limited now by
observations of radio emission from neutrino-induced showers.
