Pachypasa otus is a moth of the family Lasiocampidae first described by Dru Drury in 1773.

It is found in southern Europe (including Italy, the Balkans, and Greece), Asia Minor, Armenia, Iraq, Iran and Israel.

Recorded food plants include Cupressus, Juniperus, Thuja occidentalis and Quercus pubescens.

It was the probable source for Roman coa vestis, wild silk textiles from the isle of Kos.

This article on a moth of the family Lasiocampidae is a stub.