水麦冬科（拉丁语学名：Juncaginaceae）共有四属约25种，广泛分布在全球温带和寒带的碱滩上或淡水沼泽中，在南北半球皆有分布。中国只有水麦冬属（Triglochin）一属，1种—水麦冬（Triglochin palustre Linn.），分布在从西南到三北地区（东北、西北、华北）。

本科植物为沼生草本，有毒，具有根状茎，有的品种具块根；叶基生，线形，基部有鞘，有时浮于水面；花两性或单性，辐射对称，无苞片；花瓣6，2轮；果实为圆筒状或倒卵形。

1981年的克朗奎斯特分类法将本科分到茨藻目，2003年根据基因亲缘关系分类的APG II 分类法将其合并到泽泻目。

Juncaginaceae is a family of flowering plants, recognized by most taxonomists for the past few decades. It is also known as the Arrowgrass family.

The APG II system, of 2003 (unchanged from the APG system, of 1998), also recognizes such a family and places it in the order Alismatales, in the clade monocots. The species are found in cold or temperate regions in both the Northern and Southern Hemisphere.