地位未定（Incertae sedis）是一个分类学上的拉丁文术语，意指「所处位置不明」，也就是某一分类群与其他分类群在分类学上的大致关系尚未确定。举例而言，假如人属（Homo）是一个新发现的属，而此属与同在人科（Hominidae）中的其他属之关系未明，便可称之Incertae sedis。

Incertae sedis (Latin for "of uncertain placement") is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertainty at specific taxonomic levels is indicated by incertae familiae (of uncertain family), incerti subordinis (of uncertain suborder), incerti ordinis (of uncertain order) and similar terms.