Phenylmalonic acid, also known as benzene-1,3-dicarboxylic acid, is an organic compound with the chemical formula C9H8O4. It exists as white crystals and is utilized as a precursor in the synthesis of pharmaceuticals, agrochemicals, and specialty chemicals. Phenylmalonic acid serves as a critical intermediate in organic chemistry due to its ability to participate in diverse chemical reactions, making it an essential building block for a wide range of valuable compounds.