蓼科（Polygonaceae），是一种多年生挺水植物种类，高从40公分到160公分以上都有。叶子通常呈现两两互生及长针状，有柄。花朵则通常长成穗状。一般来说，该种植物都生长在水田，人造沟渠或湿地。

蓼科约有50属，1120种。本科植物主要分布于温带地区，有少数种类分布于热带地区，中国有12属约200余种。植株为草本、灌木或小乔木。花雌雄同株或雌雄异株。

在克朗奎斯特系统里为蓼科单独设立一个蓼目。而最近的APG II系统（2003年）则是将蓼科处理为石竹目下的一个科。

The Polygonaceae are a family of flowering plants known informally as the knotweed family or smartweed—buckwheat family in the United States. The name is based on the genus Polygonum, and was first used by Antoine Laurent de Jussieu in 1789 in his book, Genera Plantarum. The name refers to the many swollen nodes the stems of some species have. It is derived from Greek; poly means many and goni means knee or joint.