Basic lead phosphite is an inorganic compound with the proposed composition Pb<sub>3</sub>O(OH)<sub>2</sub>(HPO<sub>3</sub>). The compound contains the phosphite anion, which provides the reducing properties associated with the application of this material.
It is widely used as a stabilizer for chlorine-containing polymers, especially polyvinylchloride. Other lead phosphites are known, including normal lead phosphite, PbHPO<sub>3</sub>, although the basic salt is especially effective.