In grammar, genitive (abbreviated gen; also called the possessive case or second case) is the grammatical case that marks a noun as modifying another noun. It often marks a noun as being the possessor of another noun but it can also indicate various relationships other than possession; certain verbs may take arguments in the genitive case; and it may have adverbial uses (see Adverbial genitive).

Placing the modifying noun in the genitive case is one way to indicate that two nouns are related in a genitive construction. Modern English typically does not morphologically mark nouns for a genitive case in order to indicate a genitive construction; instead, it uses either the 's clitic or a preposition (usually of). However, the personal pronouns do have distinct possessive forms. There are various other ways to indicate a genitive construction, as well. For example, many Afroasiatic languages place the head noun (rather than the modifying noun) in the construct state.

Depending on the language, specific varieties of genitive-noun–main-noun relationships may include: