Aethusa cynapium (fool's parsley, fool's cicely, or poison parsley) is an annual (rarely biennial) herb in the flowering plant family Apiaceae, native to Europe, western Asia, and northwest Africa.

[2] It has a fusiform root and a smooth hollow branched stem growing to about 80 cm (31 in) high, with much divided (ternately pinnate) smooth leaves with an unpleasant smell, and small compound umbels of small irregular white flowers.

A. cynapium's toxic effects are caused at least in part by cynopine, which resembles coniine in its physical and chemical characters as well as physiological actions.

The plants has been used in traditional medicine to treat complaints in children, infantile cholera, summer diarrhea, convulsions, mental tension, sleep disorders, delirium, and as stomachic.

A post-mortem examination has shown redness of the membrane lining the gullet and windpipe, along with symptoms of slight congestion within the duodenum and stomach.