Abstract The reverse water‐gas shift reaction (RWGS) has been regarded as a promising approach for fighting climate change caused by the excessive emission of the greenhouse gas CO 2 , but it still suffers from relatively poor low‐temperature reactivity. Herein, a high‐performance RWGS catalyst composed of ultrasmall Pt clusters (1.38 nm on average) anchored by La 2 O 2 CO 3 support (Pt NC /LOC), which possesses a record CO production rate of 2678 mol CO mol Pt −1 h −1 with nearly 100% CO selectivity at 300 °C, is reported. The specific activity is nearly 1.5 and 7.9 fold higher than that of Pt single atoms and nanoparticles on La 2 O 2 CO 3 , respectively. More importantly, over 87.7% of the initial activity of Pt NC /LOC remains after 80 h constant operation at 380 °C, firmly verifying the structural robustness. LOC support is essential, because of not only the moderate basicity that can boost the reaction efficiency but also the strong interaction with Pt species that can stabilize the ultrasmall particle size. Further investigations also point out the key role of the Pt clusters. The two key steps, CO 2 adsorption, and CO desorption, individually prefer electron‐rich and electron‐deficient Pt species. Ultrasmall Pt clusters successfully integrate the unique surface states of single atoms and nanoparticles, thus achieving excellent low‐temperature RWGS performance.