The Mirandese language (autonym: mirandés or lhéngua mirandesa; Portuguese: mirandês or língua mirandesa) is a Romance language belonging to the Astur-Leonese linguistic group, sparsely spoken in a small area of northeastern Portugal, in the municipalities of Miranda do Douro, Mogadouro and Vimioso. The Portuguese Parliament granted it co-official recognition (along with the Portuguese language) for local matters on 17 September 1998 with the law 7/99 of 29 January 1999.

Mirandese has a distinct phonology, morphology and syntax, and has been distinct at least since the formation of Portugal in the 12th century. It has its roots in the spoken Latin of the north of the Iberian Peninsula (Portuguese developed in the northwest).

It is a descendant of the ancient Astur-Leonese language of northern Iberia, the last remnant of the ancient language of the Kingdom of León, and closely related to the modern Astur-Leonese languages in Spain. However, these amalgamations in the Spanish territory did not affect Mirandese, which preserves distinct linguistic differences in relation to both Portuguese and Spanish. It shares a great deal of lexicon with regional Portuguese dialects.

In the 19th century, José Leite de Vasconcelos described it as “the language of the farms, of work, home, and love between the Mirandese”. Since 1986–87 it has been taught to students between the ages of 10 and 11, and so is recovering.

Today Mirandese retains fewer than 5,000 speakers (but the number can be up to 15,000 if counting second-language speakers) in the villages of the Municipality of Miranda do Douro and in some eastern villages (e.g. Vilar Seco and Angueira; in Caçarelhos, it is considered recently extinct) of the Municipality of Vimioso, and some linguistic influence can be observed at other villages of the municipality of Vimioso and the municipalities of Mogadouro, Macedo de Cavaleiros and Bragança.

Three variants of the Mirandese language exist: Border Mirandese (Mirandés Raiano), Central Mirandese (Mirandés Central) and Sendinese (Sendinés). Most speakers of Mirandese also speak Portuguese; some of these speak Spanish as well.

The main differences between Mirandese in Portugal and the Astur-Leonese languages in Spain are caused by the dominant languages in each region. Mirandese has been influenced phonetically and in lexicon by Portuguese and the Astur-Leonese languages in Spain by Spanish (Castilian). All have distinctive orthography that phonetically reflects the respective main national languages. Another difference is that Mirandese and Leonese remain very conservative, while Asturian has undergone a greater amount of change.