  We show that the proposed Large Hadron electron Collider (LHeC) will provide
an opportunity to search for left-right symmetry and establish lepton number
violation, complementing current and planned searches based on LHC data and
neutrinoless double beta decay. We consider several plausible configurations
for the LHeC -- including different electron energies and polarizations, as
well as distinct values for the charge misidentification rate. Within
left-right symmetric theories we determine the values of right-handed neutrino
and gauge boson masses that could be tested at the LHeC after one, five and ten
years of operation. Our results indicate that this collider might probe, via
the $\Delta L =2$ signal $e^-p\to e^+jjj$, Majorana neutrino masses up to 1 TeV
and $W_R$ masses up to 6.5 TeV. Interestingly, part of this parameter space is
beyond the expected reach of the LHC and of future neutrinoless double beta
decay experiments.
