  We calculate the extent to which collisionless dark matter impacts the
stability of supermassive stars $(M\gtrsim10^4\,M_\odot)$. We find that,
depending on the star's mass, a dark matter content in excess of ${\sim}1\%$ by
mass throughout the entire star can raise the critical central density for the
onset general relativistic instability, in some cases by orders of magnitude.
We consider implications of this effect for the onset of nuclear burning and
significant neutrino energy losses.
