Centaurea sulphurea (Sicilian star thistle or sulphur star knapweed) is an Asteraceae annual herb species. It is native to southwestern Europe and it is known on other continents as an introduced species. It is one of the closest relatives to Centaurea solstitialis, an extremely invasive thistle in California, but Centaurea sulphurea has only established several populations in California since its introduction in the mid-19th century.