Dysschema thetis, the northern giant flag moth, is a moth of the family Erebidae.

The species was first described by Johann Christoph Friedrich Klug in 1836.

It is found from the south-western United States to north-western Mexico.

[2] The larvae feed on Asteraceae species.

[3] Dysschema thetis and Dysschema mariamne have historically been regarded as synonyms; however, the lectotype of thetis belongs to the same population historically known as D. howardi, therefore making these two synonyms, while mariamne is the correct name for the more southern species.