Tris(2,4-di-tert-butylphenyl)phosphite is an organophosphorus compound with the formula [(C4H9)2C6H3O]3P.

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.

[1] It is an approved food contact materials in the US.