Eriogaster catax, commonly known as the eastern eggar, is a species of moth in the family Lasiocampidae.

In both sexes, the front wings show a transversal line and a white discal spot within a dark border.

Females are larger and at the end of the abdomen they have a tuft of dense gray-black hairs.

The larvae feed on Crataegus, Quercus, Betula, Populus, Prunus and Berberis species.

It is found in Austria, Belgium, Bulgaria, Czech Republic, Germany, Hungary, Italy, the Netherlands, Poland, Serbia and Montenegro, Slovakia, and Spain.