Trichosirocalus horridus is a species of true weevil, native to Europe.

It is a biological pest control agent that was introduced into the United States in 1974 to control exotic thistles, especially in the Cirsium and Carduus genera.

[2][3] Trichosirocalus horridus feeds on the rosettes of thistles, with the larvae causing most damage to the plant.

In 2004, T. horridus was observed feeding on the native thistle Cirsium altissimum L. in Nebraska.

[4] T. horridus has also been observed feeding on 5 native Cirsium species in Tennessee.