The light curve, energy spectra, energetics, and IPN localization of an exceedingly intense, short-duration, hard-spectrum burst, GRB 070201, obtained from Konus-Wind, INTEGRAL (SPI-ACS), and MESSENGER data are presented. The total fluence of the burst and the peak flux are S = 2.00+ 0.10-0.26 × 10-5 erg cm-2 and Fmax = 1.61+ 0.29-0.50 × 10-3 erg cm-2 s-1. The IPN error box has an area of 446 arcmin2 and covers the peripheral part of the M31 galaxy. Assuming that the source of the burst is indeed in M31 at a distance of 0.78 Mpc, the measured values of the fluence S and maximum flux Fmax correspond to a total energy of Q = 1.5 × 1045 erg and a maximum luminosity L = 1.2 × 1047 erg s-1. These data are in good agreement with the corresponding characteristics of the previously observed giant flares from other soft gamma repeaters. The evidence for the identification of this event as a giant flare from a soft gamma repeater in the M31 galaxy is presented.