Brazilin is a natural dye that is extracted from the heartwood of South American trees Caesalpinia echinata and Haematoxylon brasiletto, and is closely related to the more well known hematoxylin, from which it differs by having one less hydroxyl group. Its oxidation to Brazilein is analogous to that dye, as is the way it forms lakes with mordants, usually aluminum or iron, although others have been suggested. The tissue component most frequently demonstrated is nuclear chromatin, which it stains red. It has not gained the popularity of the similar Hematoxylin, as it can be replaced with other, more easily available red dyes.

At least one commercial supplier suggests it as a substitute for Nuclear fast red, because of difficulties with supply of that dye. The recommendation is that Brazilin be substituted for Hematoxylin in hemalum formula, but the amount of dye used doubled. It is also noted that Brazilin must be oxidized to Brazilein with sodium iodate for the solutions to stain properly. Likely the same amount of sodium iodate would be required as for Hematoxylin.

There is an interesting article on Brazilin and Hematoxylin at Wayne's Word. The article describes how logwood dyes were introduced to Europe, and how they resulted in the creation of two countries.

Like Hematoxylin, Brazilin has not been completely synthesized.