Alkaline　water　electrolysis　(AWE)　is　a　prospective　method　for　producing　green　hydrogen　to　solve　the　energy　crisis　and　reduce　environmental　pollution.　However,　the　hydrogen　production　efficiency　through　this　process　is　exceptionally　low　because　the　electrodes　are　expensive　and　inefficient.　In　this　work,　a　kind　of　high-entropy　alloy　(HEA),　bulk　AlCoCrFeNi,　is　used　as　the　efficient　electrode　for　AWE.　Results　show　that　the　HEA　treated　by　5-min　fast　anodization　can　achieve　ultra-high　catalytic　activities　for　hydrogen　and　oxygen　evolution　reactions　with　low　overpotentials　of　880　and　845　mV　to　reach　the　current　densities　of　−500　and　500　mA　cm−2,　respectively.　For　full　water　splitting,　it　only　needs　3.00　V　and　exhibits　excellent　stability　of　more　than　100　h　at　500　mA　cm−2.　Our　study　demonstrates　that　the　anodized　AlCoCrFeNi　HEA　has　promising　applications　as　a　highly　efficient　catalyst　in　industrial　water　electrolysis　for　hydrogen　production,　potentially　addressing　the　energy　crisis　and　environmental　concerns.　[Figure　not　available:　see　fulltext.]　©　2022,　Science　China　Press　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature.