Oil Blue 35[1] is a blue anthraquinone dye used for colouring alcoholic and hydrocarbon based solvents, including oils, fats, and waxes.

In some countries, it is used as a fuel dye.

It is also used in some blue colored smoke formulations.

In microscopy, it is used as a staining dye.

When exposed to 5% hydrochloric acid solution, it becomes dirty green.