The nominative case (abbreviated NOM) is one of the grammatical cases of a noun or other part of speech, which generally marks the subject of a verb or the predicate noun or predicate adjective, as opposed to its object or other verb arguments. Generally, the noun "that is doing something" is in the nominative, and the nominative is the dictionary form of the noun.

Nominative comes from Latin cāsus nominātīvus "case for naming", which was translated from Ancient Greek ptôsis onomastikḗ "inflection for naming", from onomázō "call by name", from ónoma "name".Dionysius Thrax in his Art of Grammar refers to it as orthḗ or eutheîa "straight", in contrast to the oblique or "bent" cases.

The reference form (more technically, the least marked) of certain parts of speech is normally in the nominative case, but this is often not a complete specification of the reference form, as it may also be necessary to specify such as the number and gender. Thus the reference or least marked form of an adjective might be the nominative masculine singular. The parts of speech which are often declined and therefore may have a nominative case are nouns, adjectives, pronouns and less frequently numerals and participles. The nominative case often indicates the subject of a verb but sometimes does not indicate any particular relationship with other parts of a sentence. In some languages the nominative case is unmarked, it may be said to be marked by a zero morpheme. Moreover, in most languages with a nominative case, the nominative form is the lemma; that is, it is the reference form used to cite a word, to list it as a dictionary entry, etc..