In linguistics, inalienable possession (abbreviated INAL) is a type of possession in which a noun is obligatorily possessed by its possessor. Nouns or nominal affixes in an inalienable possession relationship cannot exist independently or be "alienated" from their possessor. Inalienable nouns include body parts (such as leg, which is necessarily "someone's leg" even if it is severed from the body), kinship terms (such as mother), and part-whole relations (such as top). Many languages reflect the distinction but vary in how they mark inalienable possession. Cross-linguistically, inalienability correlates with many morphological, syntactic, and semantic properties.

In general, the alienable–inalienable distinction is an example of a binary possessive class system in which a language distinguishes two kinds of possession (alienable and inalienable). The alienability distinction is the most common kind of binary possessive class system, but it is not the only one. Some languages have more than two possessive classes. In Papua New Guinea, for example, Anêm has at least 20 classes, and Amele has 32.

Statistically, 15–20% of the world's languages have obligatory possession.