  The dark matter annihilation cross section can be amplified by orders of
magnitude if the annihilation occurs into a narrow resonance, or if the
dark-matter particles experience a long-range force before annihilation
(Sommerfeld effect). We show that when both enhancements are present they
factorize completely, that is, all long-distance non-factorizable effects
cancel at leading order in the small-velocity and narrow-width expansion. We
then investigate the viability of ``super-resonant'' annihilation from the
coaction of both mechanisms in Standard Model Higgs portal and simplified
MSSM-inspired dark-matter scenarios.
