植物分类学是一门研究如何描述、鉴定、命名及分类植物科学，且可能是植物科学最古老的一个分支。其研究的对象为分类群 (taxa)。

植物分类学和植物系统学之间有着密切的关联，自1980年代之后，更多更广的涵盖范围，使许多学者倾向使用植物系统学这个名称，或认为分类学是包含在系统学之中。实务上，「植物系统学」比植物分类学特别注意到这些分类群之演化与不同分类群之间的关系。

Plant taxonomy is the science that finds, identifies, describes, classifies, and names plants. Thus making it one of the main branches of taxonomy(the science that finds, describes, classifies, and names living things).

Plant taxonomy is closely allied to plant systematics, and there is no sharp boundary between the two. In practice, "Plant systematics" involves relationships between plants and their evolution, especially at the higher levels, whereas "plant taxonomy" deals with the actual handling of plant specimens. The precise relationship between taxonomy and systematics, however, has changed along with the goals and methods employed.