Izatha lignyarcha is a moth of the Oecophoridae family. It is endemic to New Zealand, where it is known only from higher altitudes on the North Island volcanoes (Mount Taranaki and Mount Ruapehu), except for one specimen from Taupo and one from Masterton. The wingspan is 24.5–30 mm for males and 24–31 mm for females. Adults have been recorded in November, December, January and February.