  We report and characterize a white-light superflare on a previously
undiscovered M dwarf detected by the ASAS-SN survey. Employing various
color-magnitude and color-spectral type relationships, we estimate several
stellar parameters, including the quiescent V-band magnitude, from which we
derive a flare amplitude of $\Delta V \sim 10$. We determine an r-band absolute
magnitude of $M_{r} = 11.4$, consistent with a mid-M dwarf, and an approximate
distance to the source of $2.2$ kpc. Using classical-flare models, we infer a
flare energy of $E_{V} \simeq (4.1\pm 2.2)\times 10^{36}$ ergs, making this one
of the strongest flares documented on an M dwarf.
