We demonstrate a new approach to synthesizing high-activity electrocatalysts for the O₂reduction reaction with ultra low Pt content. The synthesis involves placing a small amount of Pt, the equivalent of a monolayer, on carbon-supported niobium oxide nanoparticles (NbO₂ or Nb₂O₅). Rotating disk electrode measurements show that the Pt/NbO₂/C electrocatalyst has three times higher Pt mass activity for the O₂reduction reaction than a commercial Pt/C electrocatalyst. The observed high activity of the Pt deposit is attributed to the reduced OH adsorption caused by lateral repulsion between PtOH and oxide surface species. The new electrocatalyst also exhibits improved stability against Pt dissolution under a potential cycling regime (30 000 cycles from 0.6 V to 1.1 V). These findings demonstrate that niobium-oxide (NbO₂) nanoparticles can be adequate supports for Pt and facilitate further reducing the noble metal content in electrocatalysts for the oxygen reduction reaction.