Aureolin (sometimes called cobalt yellow) is a pigment sparingly used in oil and watercolor painting.

It was first made in 1831 by Nikolaus Wolfgang Fischer in Breslau characterizing it as "Doppelsalze" or double-salts[1] and its chemical composition is potassium cobaltinitrite.

[4] The investigation by Gates gives the exact modern procedures for the preparation of aureolin and also the methods for its identification in paintings.

It is a rather expensive pigment and sold by several manufacturers of oil paints such as Grumbacher, Michael Harding, and Holbein.

However, the pigment was never popular as an oil color and is much more widely available as a watercolor from manufacturers such as: Winsor & Newton, Talens Rembrandt, Rowney Artists, Sennelier, Art Spectrum and Daniel Smith.