The advancement of contemporary X-ray imaging heavily depends on discovering scintillators that possess high sensitivity, robust stability, low toxicity, and a uniform size distribution. Despite significant progress in this field, the discovery of a material that satisfies all of these criteria remains a challenge. In this study, we report the synthesis of monodisperse copper(I)-iodide cluster microcubes as a new class of X-ray scintillators. The as-prepared microcubes exhibit remarkable sensitivity to X-rays and exceptional stability under moisture and X-ray exposure. The uniform size distribution and high scintillation performance of the copper(I)-iodide cluster microcubes make them suitable for the fabrication of large-area, flexible scintillating films for X-ray imaging applications in both static and dynamic settings.