Idaea inquinata, the rusty wave, is a moth of the family Geometridae. It is found in Europe.

The species has a wingspan of 16–19 mm. The length of the forewings is 8–10 mm. The adults fly at night from June to July [1] in Britain. The species is a rare and introduced species in England and The Netherlands and probably came to these countries with imported dried flowers and herbs.

1. ^ The flight season refers to the British Isles. This may vary in other parts of the range.