  The Standard Model electroweak vacuum has been found to be metastable, with
the true stable vacuum given by a large, phenomenologically unacceptable vacuum
expectation value $\approx M_{P}$. Moreover, it may be unstable in an
inflationary universe. Motivated by the necessity of physics beyond the
Standard Model and to accommodate non-zero neutrino masses, we investigate
vacuum stability within type-II seesaw and left-right symmetric models. Our
analysis is performed by solving the renormalisation group equations, carefully
taking into account the relevant threshold corrections. We demonstrate that a
phenomenologically viable left-right symmetric model can be constructed by
matching it with the SM at one-loop. In both models we demonstrate the
existence of a large area of parameter space where the Higgs vacuum is
absolutely stable.
