We report observation of the piezoresistive effect of β-Ga 2 O 3 and investigate its application for strain gauge sensors. Ti/Au ohmic contacts are fabricated on commercially procured β-Ga 2 O 3 materials. We employ the transfer length measurement pattern to remove the influence of contact resistance on the resistance measurement of β-Ga 2 O 3 samples, especially when measuring the relatively small piezoresistance change due to strain. A gauge factor of −5.8 ± 0.1 is measured from a Ti/Au-β-Ga 2 O 3 -Ti/Au structure under tensile uniaxial stress in the [010] direction at room temperature.