Middle Irish, also called Middle Gaelic (Irish: An Mheán-Ghaeilge, Scottish Gaelic: Meadhan-Ghàidhlig, Manx: Mean Ghaelg), is the Goidelic language which was spoken in Ireland, most of Scotland and the Isle of Man from c. 900–1200 AD; it is therefore a contemporary of Late Old English and Early Middle English. The modern Goidelic languages—Modern Irish, Scottish Gaelic and Manx Gaelic—are all descendants of Middle Irish.

Middle Irish is a fusional, VSO, nominative-accusative language, and makes frequent use of lenition.

Nouns decline for two genders: masculine and feminine, though traces of neuter declension persist; three numbers: singular, dual, plural; and five cases: nominative, accusative, genitive, prepositional, vocative. Adjectives agree with nouns in gender, number, and case.

Verbs conjugate for three tenses: past, present, future; four moods: indicative, subjunctive, conditional, imperative; independent and dependent forms. Verbs conjugate for three persons and an impersonal, agentless form (agent). There are a number of preverbal particles marking the negative, interrogative, subjunctive, relative clauses, etc.

Prepositions inflect for person and number. Different prepositions govern different cases, depending on intended semantics.

The following is an untitled poem in Middle Irish about Eógan Bél, King of Connacht.