A hypostasis, from the Greek word ὑπόστασις meaning foundation, base or that which stands behind is a term in linguistics to describe the relationship between a name and a known quantity, as a cultural personification (i.e. objectification with personality) of an entity or quality. It often connotes the personification of typically elemental powers, such as wind and fire, or human life, fertility, and death.

The term "hypostasis" is considered to be scientifically and culturally neutral, for the purpose of describing name-to-term relationships that, within religion and theology might be termed a "deification," or otherwise by the more pejorative "idolatry." The concept of "hypostasis" functions as a kind of conceptual inverse for terms which may have originated as personal names, and have linguistically evolved to become common terms for general concepts and qualities.

The ethymologically corresponding Latin word is substantia, i.e. substance; however especially in the context of Christian theology it is usually translated into Latin as persona, i.e. person.

The Christian view of the trinity is often described as a view of one God existing in three different hypostases. The word is used prominently in the original Greek version of the Nicene Creed in this sense.