  We present a study of white light flares from the active M5.5 dwarf Proxima
Centauri using the Canadian microsatellite MOST. Using 37.6 days of monitoring
data from 2014 and 2015, we have detected 66 individual flare events, the
largest number of white light flares observed to date on Proxima Cen. Flare
energies in our sample range from $10^{29}$-$10^{31.5}$ erg. The flare rate is
lower than that of other classic flare stars of similar spectral type, such as
UV Ceti, which may indicate Proxima Cen had a higher flare rate in its youth.
Proxima Cen does have an unusually high flare rate given its slow rotation
period, however. Extending the observed power-law occurrence distribution down
to $10^{28}$ erg, we show that flares with flux amplitudes of 0.5% occur 63
times per day, while superflares with energies of $10^{33}$ erg occur ~8 times
per year. Small flares may therefore pose a great difficulty in searches for
transits from the recently announced 1.27 M_earth Proxima b, while frequent
large flares could have significant impact on the planetary atmosphere.
