Dyes can be classified as either natural or synthetic. The only natural dye still used on a large scale is logwood, which imbues silk, wool, cellulose acetate, and nylon with a deep black colour. With the exception of a few inorganic materials used in special processes, all dyestuffs used in textile applications are synthetic organic chemicals.

Synthetic dyes can be classified according to either their characteristics or their application to textiles. Manufacturers of dyes usually classify dyes according to their chemical structure, whereas dyers generally classify dyes based on the method of application.

According to the dyers' method of classification, there are direct dyes, which produce fast colours in fibres placed directly in the dye solutions, and indirect dyes, which produce fast colours only if the fibres are treated before or after dyeing.