Chamerion angustifolium, commonly known in North America as fireweed, in some parts of Canada as great willowherb, and in Britain as rosebay willowherb, is a perennial herbaceous plant in the willowherb family Onagraceae. It is native throughout the temperate Northern Hemisphere, including large parts of the boreal forests. Two subspecies are recognized as valid: * Chamerion angustifolium subsp. angustifolium * Chamerion angustifolium subsp. circumvagum (Mosquin) Hoch