Plectophila thrasycosma is a moth in the family Xyloryctidae.

There is an oblique fascia rising from this at one-fourth, the posterior edge obtusely angulated, expanded on the dorsum so as to extend nearly from the middle to the tornus.

There is also an irregular fascia running from the costal streak beyond the middle almost or quite to touch this at the tornus, then abruptly angulated upwards and running near the termen to the apex, with a more or less distinct prominence touching the termen in the middle.

The hindwings are light grey tinged with whitish ochreous.

They feed from within a spiral tunnel of silk and frass in the leaves.