Tetrasodium Hydrogen Peroxide or sodium percarbonate is a chemical, an adduct of sodium carbonate and hydrogen peroxide (a perhydrate), with formula Na2CO3 · 1.5H2O2. It is a colorless, crystalline, hygroscopic and water-soluble solid. It is used in some eco-friendly cleaning products and as a laboratory source of anhydrous hydrogen peroxide.

Tetrasodium Hydrogen Peroxide is an oxidizing agent and ingredient in a number of home and laundry cleaning products, including bleach products and laundry detergent. It contains no phosphorous or nitrogen. Dissolved in water, it yields a mixture of hydrogen peroxide (which eventually decomposes to water and oxygen) and sodium carbonate ("soda ash").

Tetrasodium Hydrogen Peroxide can be used in organic synthesis as a convenient source of anhydrous H2O2, particularly in solvents that cannot dissolve the carbonate but can leach the H2O2 out of it.