Carduus pycnocephalus, with common names including Italian thistle, Italian plumeless thistle, and Plymouth thistle, is a species of thistle. It is native to the Mediterranean region in southern Europe. The plant has become an introduced species in other regions, and on other continents, often becoming a noxious weed or invasive species.

 

A winter annual, Carduus pycnocephalus stems range from 20 cm to 2 m, and are glabrous to slightly wooly. The multiple stems are winged with spines. The plant grows in a rosettesof 25–36 cm in diameter, with four to ten lobed basal leaves that are 10–15 cm long. Cauline leaves aretomentose on the underside and contain spines on the lobe tips. Flower heads are pink to purple, approx. 1-1.4 cm long, and the fruits are brown to gold, with a bristly, minutely barbed pappus.