Pt-Nb2O5 porous composite ceramics have been prepared from Pt and Nb2O5 particles through convenient pressing and sintering. Extraordinary room-temperature hydrogen sensing capabilities have been revealed for Pt-Nb2O5 composite ceramics of 1 wt% Pt, including a sensitivity over 165, response time and recovery time of 7s and 39s, respectively, for 1% H-2 in air. For 0.25% and lower concentrations of H-2 in air, ultrafast recoveries, such as a recovery time of 8s for 0.04% H-2 in air, are observed, which are singular for room temperature hydrogen sensing. We further found a strong correlation between the resistance of Pt-Nb2O5 composite ceramics and hydrogen concentration in ambient oxygen free atmospheres, and a negative temperature dependence of hydrogen sensitivity, from which a hydrogen sensing mechanism rooted in hydrogen chemisorption on Nb2O5 has been established, while the ultrafast recoveries are explained in terms of a highly mobile and reactive state of chemisorbed hydrogen ions on Nb2O5. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.