As　a　promising　two-dimensional　conjugated　polymer,　graphitic　carbon　nitride　(g-C3N4)　has　been　utilized　as　a　low-cost,　robust,　metal-free,　and　visible-light-active　photocatalyst　in　the　field　of　solar　energy　conversion.　This　Review　mainly　describes　the　latest　advances　in　g-C3N4　photocatalysts　for　water　splitting.　Their　application　in　CO2　conversion,　organosynthesis,　and　environmental　purification　is　also　briefly　discussed.　The　methods　to　modify　the　electronic　structure,　nanostructure,　crystal　structure,　and　heterostructure　of　g-C3N4,　together　with　correlations　between　its　structure　and　performance　are　illustrated.　Perspectives　on　the　challenges　and　opportunities　for　the　future　exploration　of　g-C3N4　photocatalysts　are　provided.　This　Review　will　promote　the　utilization　of　g-C3N4　materials　in　the　fields　of　photocatalysis,　energy　conversion,　environmental　remediation,　and　sensors.　©　2015　WILEY-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.