Low-energy ion-induced breakdown and single-event burnout are experimentally observed in β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Schottky diodes with voltages well below those of expected electrical breakdown. Fundamentally different responses were observed among alpha-particle, Cf-252, and heavy-ion irradiation. TCAD simulations suggest that ion-induced burnout can be triggered at high voltages as a result of a single ion strike, leading to impact ionization, voltage-induced charge separation accentuated by the low intrinsic hole mobility in β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , and breakdown. At significantly lower voltages, the cumulative buildup of displacement-damage-induced defects in β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> during high-fluence ion irradiation can lead to defect-driven breakdown due to the generation and motion of negatively charged Ga vacancies and O interstitials. First-principles calculations show that defect clusters can be formed that are much less resistive than the surrounding material. These clusters can be driven deeply into the device by the reverse bias, ultimately forming conduction paths that can facilitate the destruction of the device at reduced voltages.