We report a highly efficient Pd/Ni(OH)₂ catalyst loaded with ultra-low levels of palladium (50 ppm Pd by mass) for the selective hydrogenation of acetylene to ethylene. The turnover frequency for acetylene conversion over the 0.005% Pd/Ni(OH)₂ catalyst is twice that of the equivalent 0.8% Pd/Ni(OH)₂ catalyst. Notably, an acetylene-to-ethylene selectivity of 80% was achieved over a wide range of temperatures. Aberration-corrected high-angle annular dark-field scanning transmission electron microscopy was used to reveal the atomically dispersed nature of palladium in the 0.005% Pd/Ni(OH)₂ catalyst. The excellent selectivity of this catalyst is attributed to its atomically dispersed Pd sites, while the abundant hydroxyl groups of the support significantly enhance the acetylene conversion activity. This work opens up innovative opportunities for new types of highly efficient catalysts with trace noble-metal loadings for a wide variety of reactions.