Possessive determiners (from Latin: possessivus; Ancient Greek: κτητικός / ktētikós - en. ktetic Lallu) are determiners which express possession. Some traditional grammars of English refer to them as possessive adjectives, though they do not have the same syntactic distribution as bona fide adjectives.

Examples in English include possessive forms of the personal pronouns, namely: my, your, his, her, its, our and their, but excluding those forms such as mine, yours, ours, and theirs that are used as possessive pronouns but not as determiners. Possessive determiners may also be taken to include possessive forms made from nouns, from other pronouns and from noun phrases, such as John's, the girl's, somebody's, the king of Spain's, when used to modify a following noun.

In many languages, possessive determiners are subject to agreement with the noun they modify, as in the French mon, ma, mes, respectively the masculine singular, feminine singular and plural forms corresponding to the English my.