An efficient ruthenium-catalyzed synthesis of tri-substituted 1,3,5-triazinones from alcohols and guanylureas under mild conditions has been developed. The scope of both the alcohols and guanylureas in the reaction is demonstrated. This ruthenium-catalyzed ring-forming process can be successfully extended to 2-guanidinobenzimidazoles to afford substituted dihydro[1,3,5]triazino[1,2-a]benzimidazoles.