Alisma plantago-aquatica, also known as European water-plantain, common water-plantain or mad-dog weed, is a perennial flowering plant widespread across most of Europe and Asia from Portugal and Morocco to Japan, Kamchatka and Vietnam. It is also regarded as native in northern and central Africa as far south as Tanzania. It is reportedly naturalized in southern Africa, Australia, New Zealand, Alaska, British Columbia, Washington State and Connecticut. Some sources maintain that the species is widespread across North America, but these reports appear to have been based on misidentified specimens. It is found on mud or in fresh waters.