Because of their moderate penetration power, β-rays (high-energy electrons) are a useful signal for evaluating the surface contamination of nuclear radiation. However, the development of β-ray scintillators, which convert the absorbed high-energy electrons into visible photons, is hindered by the limitations of materials selection. Herein, we report two highly luminescent zero-dimensional (0D) organic–inorganic lead-free metal halide hybrids, (C₁₃H₃₀N)₂MnBr₄ and (C₁₉H₃₄N)₂MnBr₄, as scintillators exhibiting efficient β-ray scintillation. These hybrid scintillators combine the superior properties of organic and inorganic components. For example, organic components that contain light elements C, H, and N enhance the capturing efficiency of β particles; isolated inorganic [MnBr₄]²⁻ tetrahedrons serve as highly localized emitting centers to emit intense radioluminescence (RL) under β-ray excitation. Both hybrids show a narrow-band green emission peaked at 518 nm with photoluminescence quantum efficiencies (PLQEs) of 81.3% for (C₁₃H₃₀N)₂MnBr₄ and 86.4% for (C₁₉H₃₄N)₂MnBr₄, respectively. To enable the solution processing of this promising metal halide hybrid, we successfully synthesized (C₁₃H₃₀N)₂MnBr₄ colloidal nanocrystals for the first time. Being excited by β-rays, (C₁₃H₃₀N)₂MnBr₄ scintillators show a linear response to β-ray dose rate over a broad range from 400 to 2,800 Gy·s⁻¹, and also display robust radiation resistance that 80% of the initial RL intensity can be maintained after an ultrahigh accumulated radiation dose of 240 kGy. This work will open up a new route for the development of β-ray scintillators.