Sudan Black is an azo dye.[1] It is nonfluorescent, relatively thermostable lysochrome (fat-soluble dye) diazo dye used for staining of neutral triglycerides and lipids on frozen sections and some lipoproteins on paraffin sections.

It has the appearance of a dark brown to black powder with maximum absorption at 596–605 nm and melting point 120–124 °C. It stains blue-black.