Oenanthe fistulosa, tubular water-dropwort, is a flowering plant in the carrot family, native to Europe, North Africa and western parts of Asia.

Each flower has 5 unequal petals with the larger, outer ones radiating, 5 stamens and 2 prominent styles arising from a swollen base (stylopodium) at the top of the ovary.

[2][1] The scientific name for tubular water-dropwort was coined by Peter Artedi, who developed the modern binomial classification system, and defined the species on the basis of its involucral characters.

[3] It was published after Artedi's death by Linnaeus in Species Plantarum, in 1753, and that name still stands, although numerous others (synonyms) have been proposed over the years, including Phellandrium fistulosum (L.) Clairv.

In Britain and Ireland it is found mainly in the lowland eastern counties, becoming increasingly rare towards the uplands of the north and west.

[10][11] In France, it is similarly considered unthreatened nationally, but in some reasons it is declining, notably in Limousin, where it is Critically Rare (CR), and Midi-Pyrénées, where it is Endangered (EN).

This decrease appears to have continued in some English counties, such as Kent, where the number of sites has shrunk by 60% between the 1970s and 2005, despite it being a Biodiversity Action Plan species.

[7] It is a wetland plant, occurring naturally in swamps and marshes along valleys and in river deltas such as the Camargue in France[13] and the Doñana National Park in Spain.

In some places it is found as a halophyte in coastal dune slacks or brackish grazing marshes, as at Aiguamolls de l'Empordà in Spain[15] or on the Sefton Coast in Britain.

[16][17] It favours clean, mesotrophic water, slightly base-rich conditions, and moderately high light levels, which make it an axiophyte in most British counties.

[21] However, when a species-poor ditch in an area of arable farmland in Romney Marsh was cleared and planted up, O. fistulosa thrived for at least a while, showing that it is not as sensitive to nutrient enrichment as some species.

It is used in traditional medicine in Algeria and investigations into the essential oil show there are constituents that could have medical benefits as well as a chemical, Heneicosane, which attracts mosquitoes involved in transmitting Dengue fever.