<p>Propane non-oxidative dehydrogenation (PDH) has become a pivotal route for propylene production, yet developing highly active, selective and stable non-noble metal catalysts remains a grand challenge. Herein, we rationally construct a series of <i>γ</i>-Al₂O₃ supported vanadium catalysts with well-defined vanadium species sizes via a facile wet impregnation method by tuning vanadium loadings. Systematic characterizations confirm that vanadium dispersion, local coordination environment, valence state and acidic properties can be precisely regulated by vanadium size engineering. The single-atom V_sa/Al₂O₃ catalyst features atomically dispersed vanadium sites without V–V bonds, strong V–O–Al metal-support interactions, low-valence V³⁺/V⁴⁺ species and weak Lewis acidity. In non-oxidative PDH, V_sa/Al₂O₃ exhibits high catalytic performance with ~ 25% propane conversion, nearly 100% propylene selectivity and long-term stability, far exceeding cluster and nanoparticle counterparts. Kinetic studies reveal that single-atom vanadium sites afford the lowest apparent activation energy (163&#xa0;kJ·mol⁻¹), while TGA results verify significantly suppressed coke formation (only ~ 4 wt% coke deposition) due to inhibited side reactions. This work demonstrates that vanadium size engineering effectively optimizes the active site structure and electronic properties, and the atomically dispersed vanadium catalyst stabilized by strong metal-support interactions serves as a promising candidate for efficient and stable PDH. These findings provide a rational strategy for designing high-performance vanadium-based catalysts for alkane dehydrogenation.</p> Graphical abstract <p></p>