Oncocera semirubella, the rosy-striped knot-horn, is a small moth of the family Pyralidae.
It is found in European regions, including the British Isles, and East Asia (e.g. China, Japan, South Korea and Taiwan).
The wingspan is 26–30 mm. The adult moth flies in one generation by the end of June to August. It is easily disturbed on short grassland, flies from dusk onwards, and is attracted to light and sugar.
The larvae feed on bird's-foot trefoil (Lotus corniculatus), white clover, Ononis species, horseshoe vetch and Medicago species.