Aristolochia rotunda, commonly known as smearwort or round-leaved birthwort, is a herbaceous perennial plant native to Southern Europe.

The solitary flowers have an unpleasant odor and they are tubular, about 2.5–5 centimetres (0.98–1.97 in) long, yellowish-green with a prominent, dark-brown or dark purple flap, both arising from the axils of the leaves.

Eating the leaves of the plant the larvae this insect ingest aristolochic acid that make them poisonous to birds.

These plants occur along the banks of canals, edges of ditches and fields, sides of roads, meadows, slopes and forests.

They prefer chalky soils and moist, shady areas, at an altitude of 0–800 metres (0–2,625 ft) above sea level.