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Strengthening OH adsorption on electrocatalyst is crucial to promote the rate‐determining water dissociation step of alkaline hydrogen evolution reaction (HER), whereas too‐intensified OH adsorption will poison the active sites instead. This dilemma remains one of the major challenges for improving the electrocatalysts' alkaline HER activities. Herein, a surprising finding that the strongly adsorbed OH on an ultrafine quinary PtCoCuNiZn nanoalloy can be facilely desorbed via a unique gradient OH desorption pattern is reported, which tremendously boosts its alkaline HER activity. Theoretical simulations unravel that the ultrafine PtCoCuNiZn nanoalloy possesses versatile metal sites for adsorbing OH and the strongly adsorbed OH can be gradiently transferred to desorb from the ultrafine PtCoCuNiZn nanoalloy with moderate energy barriers for each transfer step that is the gradient OH desorption. In the meanwhile, the unique gradient OH desorption mode on the ultrafine PtCoCuNiZn nanoalloy is also experimentally evidenced by the in situ Raman spectroscopy and cyclic voltammetry measurements. This finding offers a fresh opportunity to expedite the alkaline HER without compromising the OH adsorption strength on electrocatalysts, which thus maximally promotes their water dissociation properties and unlocks the full potential of their alkaline HER activities. [ABSTRACT FROM AUTHOR]