In linguistic typology, ergative–absolutive alignment is a type of morphosyntactic alignment in which the subject of an intransitive verb behaves like the object of a transitive verb, and differently from the subject of a transitive verb. Examples include Basque, Georgian, Mayan, Tibetan, Sumerian, and certain Indo-European languages (such as Pashto and the Kurdish languages and many Indo-Aryan languages like Hindustani). It has also been attributed to the Semitic modern Aramaic (also called Neo-Aramaic) languages. Ergative languages are classified into two groups: those that are morphologically ergative but syntactically behave as accusative (for instance, Basque, Pashto and Urdu) and those that, on top of being ergative morphologically, also show ergativity in syntax. Languages that belong to the former group are more numerous than those to the latter.

The ergative-absolutive alignment is in contrast to nominative–accusative alignment, which is observed in English and most other Indo-European languages, where the single argument of an intransitive verb ("She" in the sentence "She walks") behaves grammatically like the agent (subject) of a transitive verb ("She" in the sentence "She finds it") but different from the object of a transitive verb ("her" in the sentence "He likes her"). When ergative–absolutive alignment is coded by grammatical case, the case used for the single argument of an intransitive verb and the object of a transitive verb is the absolutive, and the case used for the agent of a transitive verb is the ergative. In nominative-accusative languages, the case for the single argument of an intransitive verb and the agent of a transitive verb is the nominative, while the case for the direct object of a transitive verb is the accusative.

Many languages have ergative–absolutive alignment only in some parts of their grammar (e.g., in the case marking of nouns), but nominative-accusative alignment in other parts (e.g., in the case marking of pronouns, or in person agreement). This is known as split ergativity.

An ergative language maintains a syntactic or morphological equivalence (such as the same word order or grammatical case) for the object of a transitive verb and the single core argument of an intransitive verb, while treating the agent of a transitive verb differently. Such languages are said to operate with S/O syntactic pivot.

This contrasts with nominative–accusative languages such as English, where the single argument of an intransitive verb and the agent of a transitive verb (both called the subject) are treated alike and kept distinct from the object of a transitive verb. Such languages are said to operate with S/A (syntactic) pivot.

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These different arguments are usually symbolized as follows:

The relationship between ergative and accusative systems can be schematically represented as the following: