<p>Conventional flat-panel X-ray detectors suffer from image distortion and non-uniformity when imaging non-planar geometries. Flexible X-ray detectors can conformally fit on a non-planar target surface and thus reduce image distortion. However, it is challenging to create thin-film transistors and photodetector backplanes that offer the necessary mechanical flexibility while maintaining good carrier mobility and photoresponsivity. Here we report a flexible active-matrix X-ray detector that has a backplane based on two-dimensional molybdenum disulfide (MoS₂) transistors and graphene/MoS₂ photodetectors. The backplane covers a large area of 3 cm × 3 cm with a total of 3,600 pixels, and exhibits a high electron mobility of 17.31 cm² V⁻¹ s⁻¹ and a photoresponsivity of 9.37 A W⁻¹ near the scintillator emission wavelength (544 nm). We use generative adversarial network-based post-processing to suppress inherent device noise, and show that the approach can provide high-quality images under lower X-ray exposure than typically needed for medical diagnosis and industrial inspection.</p>