5,5-Dimethylhydantoin is an organic compound with the molecular formula C5H8N2O2. White to off-white crystals or crystalline powder. It is derived from the reaction between cyanohydrin and ammonium carbonate aqueous solution at 50-80°C. It is used in the synthesis of amino acids, and can also be used as special epoxy resins and water-soluble resins, fungicides, preservatives, etc.