Diphenyl oxalate is an organic compound with the chemical formula (C6H5O)2C=O. It is a diester of oxalic acid and phenol, appearing as a white to off-white crystalline solid. It is a key monomer and intermediate in polymer chemistry. Its primary industrial application is as a precursor in the synthesis of high-performance engineering plastics, particularly aromatic polyesters and polyarylates. It undergoes polycondensation reactions with diols or bisphenols to produce polymers with excellent thermal stability, mechanical strength, and chemical resistance. These materials are used in automotive parts, electrical components, and specialty films. It also serves as a chemical intermediate in organic synthesis, for example, in the preparation of other esters or as a reagent in specific coupling reactions. Handling requires standard safety precautions for organic chemicals, including the use of personal protective equipment to avoid inhalation of dust and contact with skin or eyes.