We report the discovery of pressure-induced superconductivity transitions in RbMgBi, a nonmetallic layered compound under ambient conditions. Upon compression, RbMgBi first undergoes an insulator-to-metal transition at $\sim 4.5\mathrm{GPa}$, coinciding with the emergence of a superconducting phase (SC-I). A second superconducting phase (SC-II) appears near 10.4 GPa, with both phases coexisting until SC-II becomes dominant above $\sim 14\mathrm{GPa}$. High-pressure ac susceptibility confirmed the bulk superconducting nature in both phases. High-pressure x-ray diffraction reveals a substantial $c$-axis contraction and a structural transition from a tetragonal $P4$/nmm to an orthorhombic Cmcm phase near 5.5 GPa, underscoring the role of interlayer spacing in enabling superconductivity. Hall measurements show marked carrier evolution at the critical pressures, while first-principles calculations indicate a pressure-driven electronic reconstruction—from a single-band regime to a multiband state with enhanced Fermi velocity and superfluid density. Our results demonstrate a strong interplay between structural compression, carrier dynamics, and superconducting behavior, offering new insight into pressure-tuned superconductivity and guiding principles for designing emergent superconductors via coupled structural-electronic engineering.

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• Electrical conductivity
• First-principles calculations
• Hall effect
• Pressure effects
• Structural properties
• Superconductivity