苦木科为植物界之一植物科。该植物于植物分类表上，归于被子植物门（Angiospermae）双子叶植物纲（Magnoliopsida）无患子目(Sapindales) 。

本科共有十几属约100种，主要分布在热带和亚热带地区，也有生长在温带的种类，以热带美洲和非洲西部种类最多，中国有3属约10种，主要分布在长江以南，但最重要的树种—臭椿可以生长在北方直到东北南部。

本科植物一般为乔木或灌木，树皮极苦。羽状复叶互生，稀对生；花小，单性，雌雄异株或杂性，稀为两性，花瓣3～5；果实为核果、蒴果或翅果。

对本科植物的分类一直有许多争议，1998年根据基因亲缘关系分类的APG 分类法将其中传统属于本科的许多属分出为其他科，如海人树科等。

The Simaroubaceae are a small, mostly tropical, family in the order Sapindales. In recent decades, it has been subject to much taxonomic debate, with several small families being split off. A molecular phylogeny of the family was published in 2007, greatly clarifying relationships within the family. Together with chemical characteristics such as the occurrence of petroselinic acid in Picrasma in contrast to other members of the family such as Ailanthus this indicates the existence of a subgroup in the family with Picrasma, Holacantha, and Castela.