Atomically dispersed Pt species supported on Fe₂O₃ (Pt₁/Fe₂O₃) are successfully constructed by a simple ball milling process. In the selective hydrogenation of cinnamaldehyde (CAL), Pt₁/Fe₂O₃ achieves an excellent cinnamyl alcohol (COL) selectivity of 81.7% at a CAL conversion of 91.2% in pure water medium due to the superior dissociation ability of H₂ and preferential adsorption of CAL via CO.