The Dark Crimson Underwing (Catocala sponsa) is a moth in the Noctuid family. This species is a Red Data Book species in the South of Britain.The wingspan is 60–70 millimetres (2.4–2.8 in). The moth flies from July to September depending on the location. The larvae feed on oak.
This species is very similar to the Light Crimson Underwing, but the hindwing on the central cross-band is consorted into a w shape. Also this species tends to be larger, with a length of 29-34mm, and the moth is also darker, with less variation of the pattern.