Heterojunction　photocatalysts,　which　consist　of　two　or　more　semiconductors,　have　garnered　significant　attention　owing　to　their　extensive　benefits,　including　a　broad-spectrum　response,　efficient　carrier　separation　and　migration,　as　well　as　robust　redox　capabilities.　Among　the　myriad　of　semiconductors,　graphitic　carbon　nitride　(g-C3N4)　and　zinc　indium　sulfide　(ZnIn2S4)　have　been　extensively　researched　due　to　their　low　toxicity,　straightforward　and　scalable　synthesis　processes,　controllable　microstructures,　and　exceptional　chemical　stability.　Recently,　there　has　been　a　trend　towards　integrating　these　two　semiconductors　to　complement　each　other＇s　strengths.　Consequently,　a　systematic　summary　and　outlook　on　g-C3N4/ZnIn2S4　heterojunction　photocatalysts　is　both　urgent　and　valuable.　This　review　summarizes　the　advancements　in　the　g-C3N4/ZnIn2S4　heterojunctions　in　the　last　10　years.　We　first　analyzed　the　charge-transfer　mechanisms　in　the　type-I,　type-II,　Z-scheme　and　S-scheme　heterojunctions.　Then　the　typical　synthesis　methods　employed　for　creating　g-C3N4/ZnIn2S4　heterojunctions　are　introduced.　Subsequently,　we　delve　into　the　regulation　strategies　for　g-C3N4/ZnIn2S4　heterojunctions,　including　morphology　optimization,　heteroatom　doping,　defect　engineering,　and　the　construction　of　multinary　composites.　The　design　concept　and　superiorities　of　these　strategies　are　thoroughly　discussed.　Following　this,　we　systematically　showcase　the　photocatalytic　applications　of　g-C3N4/ZnIn2S4　heterojunctions,　encompassing　CO2　reduction,　H2　evolution,　pollutant　degradation,　H2O2　production,　biomass　conversion,　photoelectrochemical　sensors,　and　so　forth.　Last,　we　propose　the　challenges　that　lie　ahead　in　future　research　endeavors.　This　comprehensive　review　is　expected　to　provide　an　instructive　guideline　for　rational　design　and　applications　of　g-C3N4/ZnIn2S4　heterojunctions.　©　2025　The　Royal　Society　of　Chemistry.