Sodium pyrophosphate, also called tetrasodium pyrophosphate or tetrasodium phosphate, is a slightly toxic and mildly irritating colorless transparent crystalline chemical compound with the formula ₂₇ and CAS number 7722-88-5. It is used as a buffer, an emulsifier, and a thickening agent , and is often used as a food additive. Common foods containing sodium pyrophosphate include chicken nuggets, imitation crab , and soy-based meat alternatives.

In toothpaste, sodium pyrophosphate acts as a tartar control agent, serving to remove calcium and magnesium from saliva and thus preventing them from being deposited on teeth. Sodium pyrophosphate is sometimes used in household detergents to prevent similar deposition on clothing, but due to its phosphate content it causes eutrophication of water, promoting algae growth.