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We propose a possible explanation for the recently observed anomalous 511 keVline with a new "millicharged" fermion. This new fermion is light [${\calO}({\rm MeV})$]. Nevertheless, it has never been observed by any colliderexperiments by virtue of its tiny electromagnetic charge $\epsilon e$. Inparticular, we constrain parameters of this millicharged particle if the 511keV cosmic $\gamma$-ray emission from the galactic bulge is due to positronproduction from this new particle.

511 keV $\gamma$-ray emission from the galactic bulge by MeV millicharged dark matter