Coreus marginatus is a herbivorous species of True Bug in the family Coreidae. It is commonly known as the dock bug as it feeds on the leaves and seeds of docks and sorrels. It is a medium-sized speckled brown insect, between 13 and 15 mm long as an adult, with a broad abdomen. It occurs throughout Europe, Asia and northern Africa. It is often found in dense vegetation, such as hedgerows and wasteland.