There is a critical need for new earth-abundant phosphors to enable next-generation, highly efficient solid-state lighting. Here, we report the discovery of Sr₂LiAlO₄, the first known Sr-Li-Al-O quaternary crystal, via a carefully-targeted data-driven structure prediction and screening effort using density functional theory calculations. Sr₂LiAlO₄ is predicted and experimentally confirmed to be a thermodynamically and thermally stable phosphor host that can be excited with near-UV/blue sources. The Eu²⁺ and Ce³⁺-activated Sr₂LiAlO₄ phosphors exhibit broad emissions at l_max~ 512 nm (green-yellow) and l_max ~ 434 nm (blue), respectively, with excellent thermal quenching resistance of > 88% intensity at 150°C. A prototype phosphor-converted white LED utilizing Sr₂LiAlO₄-based phosphors yields an excellent color rendering index exceeding 90. Sr₂LiAlO₄ therefore exhibits great potential for industrial applications in low-cost, high-color-quality WLEDs.