系统发生学（希腊语：φυλογένεση，希腊语：φύλο，现代希腊语：fílo - 种系，性别和γεννήση，现代希腊语：jénnissi - 新生，诞生。英语：Phylogenetics，简称为谱系学）是指在地球历史发展过程中生物种系的发生和发展。

这个概念不单止用于动物种系的发生与发展，还会用在系统学各个层面的分类单元上面。它也会被用到某一特征的在生物发育过程中的进化这一方面。

系统发生学的研究是通过以下的手段实现的：

通过这些数据，人们就可以为生物创建一棵系统发生学树（演化树），其中描述了各个物种之间可能有的亲缘关系。

In biology, phylogenetics /ˌfaɪloʊdʒəˈnɛtɪks, -lə-/ (Greek: φυλή, φῦλον - phylé, phylon = tribe, clan, race + γενετικός - genetikós = origin, source, birth) is the study of the evolutionary history and relationships among individuals or groups of organisms (e.g. species, or populations). These relationships are discovered through phylogenetic inference methods that evaluate observed heritable traits, such as DNA sequences or morphology under a model of evolution of these traits. The result of these analyses is a phylogeny (also known as a phylogenetic tree) – a hypothesis about the history of evolutionary relationships. The tips of a phylogenetic tree can be living organisms or fossils. Phylogenetic analyses have become central to understanding biodiversity, evolution, ecology, and genomes.