Tyrian purple is a purple dye first made in the ancient city of Tyre. It was made from a secretion of various marine molluscs, such as Murex trunculus and Murex brandaris. The expensive dye was prized by Roman noblemen, who used it to colour ceremonial robes.

The main chemical constituent of the dye was discovered by Paul Friedländer in 1909 to be 6,6′-dibromoindigo, a substance that had previously been synthesized in 1903. However, it has never been synthesized commercially.

See also: Indigo dye