Fragilin is a chemical compound of the anthraquinone class.

It has the molecular formula C16H11ClO5 and is a chlorinated derivative of parietin.

In 1965, it was reported as a constituent of the lichens Sphaerophorus fragilis and Sphaerophorus coralloides.

[1] It has since been found in a variety of other lichens including Nephroma laevigatum,[2] Caloplaca,[3] Xanthoria parietina,[4] and others.