Context <p>This study employs density functional theory (DFT) to investigate the structural, electronic, transport, optical, and mechanical properties of cubic boron phosphide (c-BP), intending to elucidate its structure–property relationships. The findings reveal that c-BP exhibits an indirect bandgap of 1.93&#xa0;eV. The valence band maximum (VBM) shows triple degeneracy and pronounced dispersion, resulting in the formation of light-hole bands that provide additional transport channels for holes. A notably high hole mobility of 888.34 cm²·V⁻¹·s⁻¹ is achieved, demonstrating excellent p-type transport characteristics. Furthermore, c-BP possesses very low dielectric loss, broad optical transparency, and mechanical properties characterized by high stiffness and brittleness. This research not only deepens the mechanistic understanding of c-BP’s multifunctional behavior but also provides theoretical underpinnings for the design of advanced semiconductor devices.</p> Methods <p>All calculations were performed within the density functional theory (DFT) framework implemented in the CASTEP code, employing norm-conserving pseudopotentials. Structural relaxation used the GGA-PW91 functional, while electronic and optical properties were computed with the HSE06 hybrid functional.</p>