Carboxymethyl cellulose (CMC) or cellulose gum is a cellulose derivative with carboxymethyl groups (-CH₂-COOH) bound to some of the hydroxyl groups of the glucopyranose monomers that make up the cellulose  backbone.

CMC is a approved food ingredient classified under the E number E466. Its most widespread function in food products is the stabilization of emulsions and a viscosity modifier. It is commonly known as a thickener.

Applications range from Ice Cream to Bakery products to Chewing Gum manufacturing. Most recently, the popularity of using CMC in gluten free and low fat foods is rapidly increasing.