Thin-film transistors based on metal oxide semiconductors are essential for many unconventional electronic devices, such as flat panel displays, image sensors, medical detectors, and aerospace applications. However, the lack of a systemic understanding of the effects of X-ray irradiation on the device often limits their use in harsh space and heavy radiation environments. Here, we investigate the effects of X-ray irradiation on metal oxide thin-film transistors based on amorphous indium gallium zinc oxide (a-IGZO) and amorphous zinc tin oxide (a-ZTO) semiconductors. Under increasing doses of X-ray irradiation (1-7 kGy), a-IGZO TFTs exhibit a substantial negative shift in threshold voltage (Δ