Metal　halide　perovskites　with　broad　optical　absorption　and　long　carrier　lifetime　are　considered　as　ideal　photocatalysts.　However,　their　poor　stability　in　water　greatly　impedes　their　application　in　photocatalytic　H2　evolution　because　they　lose　their　crystalline　structure　in　water.　Herein,　we　proclaim　a　new　class　of　photocatalysts:　all-inorganic　Cs-Cu-Cl　perovskite　quantum　dots　(QDs).　It　exhibits　a　high　photocatalytic　hydrogen　production　rate　of　∼　3.1　mmol/g/h　without　any　cocatalyst　under　AM　1.5-G　solar　irradiation　(100　mW/cm2).　Especially,　it　remains　the　high　activity　for　up　to　330　h　without　apparent　deterioration　of　the　hydrogen　production　rate.　Density　functional　theory　(DFT)　calculations　reveal　that　the　Cu　site　works　as　the　electron　and　proton　absorption　sites　as　the　H2　production　active　center.　To　our　best　knowledge,　there　is　no　report　of　metal　halide　perovskites　as　water-stable　photocatalysts.　This　work　opens　an　innovative　way　for　guiding　the　exploration　of　metal　halide　perovskites　photocatalysts　for　stable　photocatalytic　H2　evolution.　©　2023　Elsevier　B.V.