Tris(2,4-di-tert-butylphenyl)phosphite is an organophosphorus compound with the formula [(C<sub>4</sub>H<sub>9</sub>)<sub>2</sub>C<sub>6</sub>H<sub>3</sub>O]<sub>3</sub>P. This white solid is a widely used stabilizer in polymers where it functions as a secondary antioxidant. It also reduces discoloration (yellowing) of plastics. The compound is a phosphite ester formed by the reaction of 2,4-di-tert-butylphenol with phosphorus trichloride. It is an approved food contact materials in the US.