Photocatalytic　hydrogen　evolution　(PHE)　from　water　splitting　is　a　promising　technology　for　clean　and　renewable　energy　production.　Elemental　crystalline　red　phosphorus　(CRP)　is　purposefully　designed　and　developed　for　PHE　reaction.　However,　the　photocatalytic　activity　of　CRP　is　limited　by　its　intrinsic　P　vacancy　(VP)　defects,　which　lead　to　detrimental　charge　trapping　at　deep　states　and　hence　its　severe　recombination.　To　address　this　issue,　a　boron　(B)　incorporated　CRP　(B-CRP)　photocatalyst　is　tailored,　synthesized　via　a　simple　and　mild　boric　acid-assisted　hydrothermal　strategy.　The　incorporation　of　B　effectively　fills　the　VP　defects,　reducing　deep　trap　states　(DTS)　and　introducing　beneficial　shallow　trap　states　(STS)　within　the　band　structure　of　CRP.　This　defect　engineering　approach　leads　to　enhanced　photocatalytic　activity,　with　B-CRP　achieving　a　PHE　rate　of　1392 µmol　g−1　h−1,　significantly　outperforming　most　reported　elemental　photocatalysts　in　the　literature.　Density　functional　theory　(DFT)　simulations　and　ultrafast　spectroscopy　support　the　constructive　role　of　B-dopant-induced　STS　in　prolonging　active　charge　carrier　lifetimes,　promoting　more　efficient　photocatalytic　reactions.　The　findings　not　only　demonstrate　the　effectiveness　of　B-CRP　as　a　photocatalyst　but　also　highlight　the　usefulness　of　dopant-induced　STS　in　advancing　PHE　technologies.　©　2024　Wiley-VCH　GmbH.