Achyranthes aspera (common names: chaff-flower, prickly chaff flower, devil’s horsewhip, Sanskrit: अपामार्ग apāmārga) is a species of plant in the family Amaranthaceae. It is distributed throughout the tropical world. It can be found in many places growing as an introduced species and a common weed. It is an invasive species in some areas, including many Pacific Islands environments.