Direct X-ray detectors are considered as competitive next-generation X-ray detectors because of their high spatial resolution, high sensitivity, and simple device configuration. However, their potential is largely limited by the imperfections of traditional materials, such as the low crystallization temperature of α-Se and the low atomic numbers of α-Si and α-Se. Here, we report the Sb₂Se₃ X-ray thin-film detector with a p–n junction structure, which exhibited a sensitivity of 106.3 μC/ (Gyair·cm²) and response time of <2.5 ms. This decent performance and the various advantages of Sb₂Se₃, such as the average atomic number of 40.8 and μτ product (μ is the mobility, and τ is the carrier lifetime) of 1.29 × 10^–5 cm²/V, indicate its potential for application in X-ray detection.