Abstract: The growing need for energy and resources is driving the search and extraction of mineral resources from deeper earth layers, resulting in significant nonlinear mechanical responses in rock masses under high ground stress. The heterogeneous nature of raw coal leads to the development of internal microcracks, which evolve into larger, visible cracks when external forces are applied. This process involves the initiation, propagation, and coalescence of internal microcracks, causing strain localization phenomena and creating localized shear zones. Such developments can lead to instability and failure of the coal samples. Triaxial compression tests on raw coal indicate a substantial drop in stress after reaching peak strength, demonstrating brittle failure characteristics under low confining pressure. As the confining pressure increases, this drop in stress gradually slows, exhibiting a shift to ductile deformation. Further research is needed at the constitutive scale to accurately describe the brittle–ductile transition in raw coal, focusing on the intrinsic physical mechanisms of coal rock damage and failure. Conventional models often overlook the relationship between the local shear zone and their surroundings, as well as the mechanical properties of these zones. As a result, simulation results may not accurately reflect the localized failure characteristics of rock materials. Recognizing localized failure in deep rock masses is crucial for engineering structural designs. This paper introduces a new elastoplastic localized damage constitutive model for raw coal based on the Mohr–Coulomb (MC) yield criterion and the mechanical behavior observed in triaxial compression mechanical responses of the rock. By applying energy equivalence principles, we can establish a relationship between internal and external mechanical variables and overall macroscopic mechanical responses. Damage variables, as an intrinsic driving variable, are used to control the expansion and contraction of the yield surface, describing both prepeak strain hardening and postpeak strain softening behaviors in raw coal. An exponential damage criterion is used to represent damage progression during rock fracturing, linking the size of localized bands to damage variables. The effectiveness of the proposed model is demonstrated by comparing numerical simulations with triaxial compression test data of raw coal. The results demonstrate that the model can capture the primary nonlinear characteristics of raw coal during triaxial compression tests. The postpeak strain softening is attributed to the rapid increase in localized damage. By controlling the evolution rate and extent of damage, the constitutive simulation results can effectively replicate the brittle–ductile transition behavior of raw coal, with the maximum level of damage decreasing exponentially as the confining pressure increases. The proposed constitutive model effectively captures the main mechanical features of localized deformation and failure of the raw coal. This enriches understanding of rock damage mechanics and introduces a fresh perspective for theoretical models in deep rock engineering.