Conjugated　carbon　nitride　(CN)　is　an　emerging　and　promising　semiconductor　photocatalyst　for　water　photolysis　owing　to　its　unique　properties.　However,　the　traditional　thermally　induced　polymerization　of　N-containing　precursors　typically　produces　melon-based　CN　solids　with　amorphous　or　semi-crystalline　structures　with　only　moderate　photocatalytic　performance.　Many　strategies　have　been　developed　to　prepare　crystalline　CNs　(CCNs),　such　as　high-temperature　and　high-pressure　routes,　ionothermal　synthesis,　and　microwave-assisted　synthesis.　In　this　Minireview,　we　summarize　the　progress　that　has　been　made　in　the　synthesis　of　CCNs　and　their　application　in　photocatalytic　water　splitting　reactions.　Three　kinds　of　CCNs　are　mainly　discussed　according　to　their　polymeric　subunits.　Challenges　associated　with　CCNs　and　their　future　development　are　also　included.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim