Catocala hermia, the Hermia underwing, is a moth of the family Erebidae. The species was first described by Henry Edwards in 1880. It is found throughout the Great Plains of North America, from southern Saskatchewan and Alberta south and west to Texas, Arizona and California.

The wingspan is 58–68 mm. Adults are on wing from August to September depending on the location.

The larvae feed on Populus and Salix species.

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