The roles of boron (B)‐layer topology in governing the stability, bonding, mechanical behavior, and pressure‐driven structural evolution of tungsten diboride (${\mathrm{WB}}_2$) were investigated using first-principles calculations, in which three representative polymorphs (hp3‐, hp6‐, and $\mathrm{hp}12\text{−}{\mathrm{WB}}_2$) were involved. By combining the analyses of formation enthalpy, elastic properties, ideal cleavage, and mechanical responses under shear and under tensile/compressive loading, and electronic structures, direct correlations between B-layer topology, bonding characteristics, and mechanical behavior were established. It was found that hp6-${\mathrm{WB}}_2$, with fully corrugated B layers, is the most stable polymorph in the ideal defect-free limit and exhibits the highest elastic stiffness and the strongest resistance to cleavage, basal shear, and tensile deformation. In contrast, $\mathrm{hp}3\text{−}{\mathrm{WB}}_2$, containing planar B layers, shows the lowest stiffness and hardness and a relatively weak tension‐compression asymmetry; and $\mathrm{hp}12\text{−}{\mathrm{WB}}_2$, composed of alternating planar and corrugated B layers, displays intermediate stability and heterogeneous mechanical behavior, with high compressive resistance but reduced tensile resistance. Electronic‐structure analysis showed that B‐layer topology modulates the directionality of B–B bonding and the degree of B‐p/W‐d hybridization, thereby controlling load-transfer pathways and failure mechanisms. Under compression, $\mathrm{hp}12\text{−}{\mathrm{WB}}_2$ does not transform into an hp6-like structure prior to instability, whereas hp6-${\mathrm{WB}}_2$ exhibits a pronounced tendency toward the planarization of B layers. These results demonstrate that B‐layer topology governs not only the stability and mechanical behavior but also topology-dependent deformation pathways, providing an insight into structure–property relationships in layered transition-metal borides.

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• Electronic structure of atoms & molecules
• First-principles calculations
• Mechanical & acoustical properties
• Borides
• Transition metals