Cortinarius orellanus, commonly known as the fool's webcap or fools webcap, is a species of deadly fungus in the family Cortinariaceae native to Europe. Within the genus it belongs to a group known as the Orellani, all of which are highly toxic—eating them results in kidney failure, which is often irreversible. The mushroom is generally tan to brown all over.

The Cortinariaceae are a large family of gilled mushrooms found worldwide, containing over 2100 species. The family takes its name from its largest genus, the varied species of the genus Cortinarius. Many genera formerly in the Cortinariaceae have been placed in various other families, including Hymenogastraceae, Inocybaceae and Bolbitiaceae.