The deformation of single-crystal beta-phase gallium oxide (or -Ga2O3) micro-pillars under compression was investigated with the aid of transmission electron microscopy. High-density stacking faults were the dominant deformation defects in the plastically deformed micro-pillars. Micro-cracks were found along (200), (001) and (010) lattice planes and fracture occurred along (200) lattice plane when compressive strain was sufficiently great. Lattice bending was also observed in the fractured pillar. The average fracture stress and strain of -Ga2O3 being measured are 7.25 +/- 1.11GPa and 3.80 +/- 0.57%, respectively, which have never been reported previously.