Propylene production via propane dehydrogenation (PDH) requires high reaction temperatures to obtain sufficient propylene yields, which results to prominent catalyst deactivation due to coke formation. Developing highly stable catalysts for PDH without deactivation even at high temperatures is of great interest and benefit for industry. Here, we report that single-atom Pt included in thermally stable intermetallic PtGa works as an ultrastable and selective catalyst for PDH at high temperatures. Intermetallic PtGa displays three-hold-Pt ensembles and single Pt atoms isolated by catalytically inert Ga at the surface, the former of which can be selectively blocked and disabled by Pb deposition. The PtGa-Pb/SiO₂ catalyst exhibits 30% conversion with 99.6% propylene selectivity at 600 °C for 96 h without lowering the performance. The single-atom Pt well catalyzes the first and second C–H activation, while effectively inhibits the third one, which minimizes the side reactions to coke and drastically improves the selectivity and stability.