The scintillator is a unique class of luminescent materials, which is of great significance in clinical diagnosis, security inspection, and radiation detection. Herein, an all-inorganic Cs 4 PbI 6 single crystals (SCs) as a nanosecond and an efficient X-ray and α particle scintillator is described. The radioluminescence (RL) spectrum of Cs 4 PbI 6 SCs under X-ray excitation consists of a band gap emission at 310 nm and a broadband emission at 552 nm at room temperature. Furthermore, Cs 4 PbI 6 SCs demonstrate nanosecond decay times of 0.95 and 6.86 ns, a high sensitivity to low-energy X-ray (30 keV) with a low detection limit (187 nGy air /s), and a favorable linearity detection range, potentially enabling their broad application in X-ray imaging. Under 237 Np α particle irradiation, the light yield of Cs 4 PbI 6 SCs is about 49.5% of that of a BGO scintillator with an energy resolution of 35% at 4.78 MeV. Our results demonstrate the potential of Cs 4 PbI 6 SCs as a nanosecond and low-cost scintillator in radiation detection applications.