禾本科（学名：Poaceae或Gramineae），禾本科主要包括稻亚科、竹亚科、早熟禾亚科等12个亚科和少数不确定类群。最近研究有668属，10000多种。中国有190余属约1200多种。除了荞麦以外，几乎所有的粮食都是禾本科植物。大自然中的野草不止是动物的食物，还能制造大量氧气，防止水土流失。

地球陆地大约有20%覆盖着草。多种俗称作“某某草”的植物是该科物种，但是必须指出，不是所有的“草”都是禾本科植物。同样，并不是所有禾本科植物都是低矮的“草”，就如竹子，也可以高达十数米，连片成林。

The Poaceae (English pronunciation: /poʊˈeɪ.siˌiː/) or Gramineae are the large and nearly ubiquitous family of monocotyledonous flowering plants known as grasses. The Poaceae include the cereal grasses, bamboos and the grasses of natural grassland and cultivated lawns (turf) and pasture. Grasses have stems that are hollow except at the nodes and narrow alternate leaves borne in two ranks. The lower part of each leaf encloses the stem, forming a leaf-sheath. With around 12,000 species, the Poaceae are the fifth-largest plant family, following the Asteraceae, Orchidaceae, Fabaceae and Rubiaceae.