naphthol, either of two colourless, crystalline organic compounds derived from naphthalene and belonging to the phenol family; each has the molecular formula C₁₀H₇OH. Both compounds have long been identified with the manufacture of dyes and dye intermediates; they also have important uses in other areas of the chemical industry.

The compound 1-naphthol, or α-naphthol, made by heating 1-naphthalenesulfonic acid with caustic alkali or by heating 1-naphthylamine with water under pressure, is used directly in making several dyes, and large amounts of it are converted to compounds ultimately incorporated into other dyes.

The compound 2-naphthol, or β-naphthol, is regarded as the most important chemical intermediate based on naphthalene. It is manufactured by fusing 2-naphthalenesulfonic acid with caustic soda and is converted into numerous dyes and dye intermediates, as well as into tanning agents, antioxidants, and antiseptics. It has been shown to be carcinogenic.