Idaea inquinata, the rusty wave, is a moth of the family Geometridae. It is found in Europe.
The species has a wingspan of 16âÂÂ19 mm. The length of the forewings is 8âÂÂ10 mm. The adults fly at night from June to July in Britain. The species is a rare and introduced species in England and is believed to have come to this country with imported dried flowers and herbs. The foodplant is believed to be dried or withered plants because of this.