Designing　high　activity　and　stable　oxygen　evolution　reaction　(OER)　catalysts　is　essential　for　improving　the　efficiency　of　the　water　splitting　reaction.　The　high　entropy　transition　metal　sulfide　(HES)　catalyst　will　be　a　promising　candidate　for　accelerating　the　OER　due　to　its　high　intrinsic　activity　and　excellent　stability.　However,　the　synthesis　of　HES　by　chemical　methods　and　the　investigation　of　the　structural　evolution　during　the　reaction　remain　a　challenging　task.　In　this　work,　a　HES　catalyst　has　been　synthesized　by　a　simple　thermal　injection　method.　All　elements　are　uniformly　distributed　in　HES　nanoparticles,　which　exhibit　excellent　activity　with　an　exceptionally　low　overpotential　of　263　at　current　densities　of　100　mA·cm−2　and　a　low　Tafel　slope　of　51.5　mV·dec−1.　This　work　demonstrates　the　great　potential　of　HES　catalysts　as　OER　electrocatalysts　and　provides　new　ideas　for　the　construction　and　extension　of　this　family　of　compounds.　©　2023　Elsevier　B.V.