  Sub-GeV thermal relic dark matter typically requires the existence of a light
mediator particle. We introduce the light two-Higgs-doublet portal, illustrated
by a minimal UV-complete model for sub-GeV dark matter with kinematically
forbidden annihilations into leptons. All new physics states in this scenario
lie at or below the electroweak scale, affecting Higgs physics, the muon
anomalous magnetic moment and potentially neutrino masses. Observation of
radiative dark matter annihilation by future MeV gamma-ray telescopes would be
key to unambiguously identify the scenario.
