In grammar, the vocative case (abbreviated VOC) is a grammatical case which is used for a noun that identifies a person (animal, object, etc.) being addressed, or occasionally for the noun modifiers (determiners, adjectives, participles, and numerals) of that noun. A vocative expression is an expression of direct address by which the identity of the party spoken to is set forth expressly within a sentence. For example, in the sentence "I don't know, John," John is a vocative expression that indicates the party being addressed, as opposed to the sentence "I don't know John" in which "John" is the direct object of the verb "know".

Historically, the vocative case was an element of the Indo-European case system and existed in Latin, Sanskrit and Greek. Many modern Indo-European languages (English, Spanish, etc.) have lost the vocative case, but others retain it, including the Baltic languages, some Celtic languages and most Slavic languages. Some linguists, such as Albert Thumb,^(de) argue that the vocative form is not a case but a special form of nouns not belonging to any case, as vocative expressions are not related syntactically to other words in sentences. Pronouns usually lack vocative forms.