Thysanura is an order of insects, encompassing silverfish and firebrats, best known for their three long caudal filaments. The name Thysanura is derived from the Greek θυσάνος, thysanos for fringe, tassel, bristle and ουρα, oura for tail, a reference to the three fanned out caudal filaments.

The families Machilidae and Meinertellidae of the jumping bristletails were once included with Thysanura. Occasionally, the correspondingly restricted order Thysanura is referred to as Zygentoma.

Silverfish are so called due to the silvery glitter of the scales covering their bodies. Their movement is "fish-like" and makes it look as if they are swimming. They are less than 1 centimetre (0.39 in) long, and found in damp corners or amongst books and paper in houses.