Platinum-based material is the most efficient and durable electrocatalyst for motivating the hydrogen evolution reaction (HER) in an acidic electrolyte; however, its low abundance and high cost limit its further application in proton-exchange membrane water electrolysis (PEMWE) technology. Therefore, minimizing the Pt amount while retaining high activity would be desirable. Herein, we use defect-rich W18O49 nanowires to anchor well-dispersed, ultrafine Pt species (Pt−W18O49) via a freeze-drying method to avoid aggregation, further mediating an efficient and durable HER in acidic water. Density functional theory analyses also demonstrate that the strong electronic interaction between the Pt species and W18O49 support greatly improves the HER performance. With a 1/10 Pt loading amount of the commercial 20 wt% Pt/C, the Pt−W18O49 catalyst requires the over-potentials of 116 and 743 mV to achieve high current densities of 100 and 1000 mA cm−2 in 0.5 mol L−1 H2SO4, outperforming those of the 20 wt% Pt/C benchmark. More importantly, the Pt−W18O49 catalyst can sustain a high-current-density HER at 500 mA cm−2 for more than 38 h without obvious degradation. This work paves a new avenue for synergistically reducing the Pt amount and retaining high activity for real-world PEMWE. [Figure not available: see fulltext.].