Vanillin is an organic compound with the molecular formula C₈H₈O₃. Its functional groups include aldehyde, ether, and phenol. It is the primary component of the extract of the vanilla bean. It is also found in roasted coffee and the Chinese red pine.

Synthetic vanillin, instead of natural vanilla extract, is sometimes used as a flavoring agent in foods, beverages, and pharmaceuticals.The largest use of vanillin is as a flavoring, usually in sweet foods. The ice cream and chocolate industries together comprise 75% of the market for vanillin as a flavoring, with smaller amounts being used in confections and baked goods.

Vanillin is also used in the fragrance industry, in perfumes, and to mask unpleasant odors or tastes in medicines, livestock fodder, and cleaning products.

Vanillin has been used as a chemical intermediate in the production of pharmaceuticals and other fine chemicals.

Additionally, vanillin can be used as a general purpose stain for developing thin layer chromatography (TLC) plates to aid in visualizing components of a reaction mixture. This stain yields a range of colors for these different components.