Mazandarani (Mazanderani: مازِرونی, Mazeruni; also spelled Mazani (مازنی) or Tabari (تبری); also called Geleki^[5])^[1] is an Iranian language of the Northwestern branch spoken by the Mazandarani people. As of 2021^[update], there were 1.36 million native speakers. The language appears to be decreasing, as it is threatened, and due to the majority of its speakers shifting to Iranian Persian.^[1] As a member of the Northwestern branch (the northern branch of Western Iranian), etymologically speaking, it is rather closely related to Gilaki and also related to Persian, which belongs to the Southwestern branch. Though the Persian language has influenced Mazandarani to a great extent, Mazandarani still survives as an independent language with a northwestern Iranian origin.^[6][7]

Mazandarani is closely related to Gilaki, and the two languages have similar vocabularies.^[8] The Gilaki and Mazandarani languages (but not other Iranian languages)^[9] share certain typological features with Caucasian languages (specifically the non-Indo-European South Caucasian languages),^[9][10][11] reflecting the history, ethnic identity, and close relatedness to the Caucasus region and Caucasian peoples of Mazandaranis and Gilak people.^{[12][13]: 295}

The name Mazanderani (and variants of it) derives from the name of the historical region of Mazandaran (Mazerun in Mazanderani), which was part of former Kingdom of Tapuria. People traditionally call their language Tabari, as the Tabari themselves do.^{[13]: 289–291}

The name Tapuri / Tabari (which was the name of an ancient language spoken somewhere in former Tapuria) is now used in preference to the name Mazandarani by the young.

However, both Gilan and Mazanderan formed part of the state known as Tapuria.

The earliest references to the language of Mazandaran, called Tabari, are to be found in the works of the early Muslim geographers. Al-Muqaddasī (or Moqaisi, 10th century), for example, notes: "The languages of Komish and Gurgan are similar, they use hā, as in hā-dih and hāk-un, and they are sweet [to the ear], related to them is the language of Tabaristan, [similar] save for its speediness."^[13]: 291

Among the living Iranian languages, Mazanderani has one of the longest written traditions, from the tenth to the fifteenth century. This status was achieved during the long reign of the independent and semi-independent rulers of Mazandaran in the centuries after the Arab invasion.^[14]

The rich literature of this language includes books such as Marzban Nameh (later translated into Persian) and the poetry of Amir Pazevari. Use of Mazanderani, however, has been in decline for some time. Its literary and administrative prominence had begun to diminish in favor of Persian by the time of the integration of Mazandaran into the national administration in the early seventeenth century.^[15]

The Mazanderani language is closely related to Gilaki and the two languages have similar vocabularies. In 1993, according to Ethnologue, there were three million native Mazanderani speakers.^[16]

The dialects of Mazanderani are Saravi, Amoli, Baboli, Ghaemshahri, Chaloosi, Nuri, Shahsavari, Ghasrani, Shahmirzadi, Damavandi, Firoozkoohi, Astarabadi and Katouli.

The native people of Sari, Shahi, Babol, Amol, Nowshahr, Chalus, and Tonekabon are Mazanderani people and speak the Mazanderani language.^[17][18]

Mazanderani is an inflected and genderless language.^[19] It is SOV, but in some tenses it may be SVO, depending on the particular dialect involved.^[20][21]

Mazanderani is commonly written in the Perso-Arabic script.^[25] However, some use the Roman alphabet, for example in SMS messages.^{[citation needed]}

Spoken in a territory sheltered by the high Alborz mountains, Mazanderani preserves many ancient Indo-European words no longer in common use in modern Iranian languages such as Persian. Listed below are a few common Mazanderani words of archaic, Indo-European provenance with Vedic cognates.

Mazandarani is rich in synonyms, some such nouns also retaining the gender they possessed in Indo-European times: for instance the words miš, gal, gerz all have the meaning of mouse, although they are not all of the same gender. While many Indo-Iranian languages use a masculine noun taking such related forms as muš or muska or mušk, in Mazandarani the most commonly used name for the mouse is the feminine noun gal.^[vague]

Another example relates to the cow, the most important animal in the symbolism of Indo-European culture: in Mazanderani there are more than 1000 recognized words used for different types of cow. The table below lists some specimens of this rich vocabulary. In Mazandaran there are even contests held to determine those with the greatest knowledge of this bovine nomenclature.

The following verses are in an eastern Mazandarani dialect spoken in the Caspian littoral in northern Iran. They were transcribed and translated by Maryam Borjian and Habib Borjian.^[28]