川蔓藻（学名：Ruppia maritima）为眼子菜科川蔓藻属下的一个种。

Ruppia maritima is a species of aquatic plant known by the common names beaked tasselweed, widgeongrass, ditch-grass and tassel pondweed. Despite its Latin name, it is not a marine plant; is perhaps best described as a salt-tolerant freshwater species. The generic name Ruppia was dedicated by Linnaeus to the German botanist Heinrich Bernhard Ruppius (1689-1719) and the specific name (maritima) translates to "of the sea".