Spin-source materials for spintronic devices are required to convert charge currents into spin currents efficiently and maintain minimal electrical losses. However, conventional strategies to enhance charge–spin conversion often come at the cost of increasing ohmic dissipation. Here we demonstrate that introducing polar lattice distortions into a highly conductive metal can overcome this trade-off. We report the discovery of polar displacements in PtCoO2 and show that these displacements enhance charge–spin conversion by two orders of magnitude compared with its non-polar phase. The coexistence of polarity and metallicity yields a room-temperature spin Hall conductivity of 1.6 × 107ℏ/2e (Ω m)−1. Electron ptychography reveals that the inversion-symmetry breaking originates from local polar nano-regions. Polar PtCoO2 drives efficient spin–orbit torque switching with substantially reduced switching voltage and power compared with Pt-based control devices, and is compatible with silicon substrates, establishing a strategy for designing highly efficient spin-source materials.