X‐ray imaging technology has attracted widespread attention due to its important application in the industrial and medical fields. The practical‐level X‐ray imager requires high‐performance scintillators with high light yield, low detection limit, superb stability, and excellent processibility. Here, a Mn2+‐doped 2D Dion‐Jacobson perovskite scintillator of (HIS)PbCl4 (HIS2+ is histammonium), is presented serving as a potential candidate for high‐resolution X‐ray imaging. By facile solution method of Mn2+‐doping, (HIS)PbCl4:2%Mn has an orange‐red emission with a high photoluminescence quantum yield (PLQY) of 80.2%. Emphatically, (HIS)PbCl4:2%Mn crystals exhibit compelling scintillation performances, including a high light yield of 77 500 photons MeV−1 (≈3.1 times of commercial Lu3Al5O12:Ce3+) and low detection limits of 59.3 nGyair s−1, along with excellent irradiation and environmental stability. Besides, both centimeter‐size single crystals and flexible scintillators fabricated with poly(dimethylsiloxane) hold a promise for practical X‐ray imaging. The high resolution using an optimized flexible scintillator screen reaches up to 20.3 lp mm−1, far beyond the most of known scintillators. The results suggest that (HIS)PbCl4:2%Mn has great commercialization potential in the field of X‐ray imaging.