The Indo-Iranian language group constitutes the easternmost extant branch of the Indo-European family of languages. It consists of three language groups: the Indo-Aryan, Iranian and Nuristani. The term Aryan languages is occasionally still used to refer to the Indo-Iranian languages. The speakers of the Proto-Indo-Iranian language, the hypothetical Proto-Indo-Iranians, are usually associated with the late 3rd millennium BC Sintashta-Petrovka culture of Central Asia. Their expansion is believed to have been connected with the invention of the chariot.

The contemporary Indo-Iranian languages form the largest sub-branch of Indo-European, with more than one billion speakers in total, stretching from Europe (Romani) and the Caucasus (Ossetian) to Xinjiang (Sarikoli) and Bangladesh. SIL in a 2005 estimate counts a total of 308 varieties, the largest in terms of native speakers being Hindustani (Hindi and Urdu, ca. 540 million), Bengali (ca. 200 million), Punjabi (ca. 120 million),
Marathi and Persian (ca. 70 million each), Gujarati (ca. 45 million), Pashto (40 million), Oriya (ca. 30 million), Kurdish (ca. 40 million) and Sindhi (ca. 20 million).

Indo-Iranian languages were once spoken across a wider area still. The Scythians were described by Roman writer Strabo as inhabiting the lands to the north of the Black Sea in present-day Ukraine, Moldova and Romania. The river-names Don, Dnieper, Danube etc. are of Indo-Iranian origin. The so-called Migration Period saw Indo-Iranian languages disappear from Eastern Europe with the arrival of the Turkic-speaking Pechenegs and others by the eighth century AD.

The oldest attested Indo-Iranian languages are Vedic Sanskrit (ancient Indian), Avestan and Old Persian (two ancient Iranian languages). But there are written instances of a fourth language in Northern Mesopotamia which is considered to be Indo-Aryan. They are attested in documents from the ancient empire of Mitanni and the Hittites of Anatolia.

Subdivisions

Iranian Group:

• Eastern Iranian

• *Northeastern

• **Avestan (extinct)

• **Scythian (extinct)

• ***Sakan (extinct)

• ***Ossetian

• ***Sarikoli

• **Sogdian (extinct)

• ***Yaghnobi

• **Bactrian (extinct)

• *Southeastern

• **Pashto

• **Pamiri

• **Ormurri-Parachi

• Western Iranian

• *Northwestern

• **Dari language of Zoroastrians

• **Balochi

• **Gilaki

• **Kurdish

• **Mazanadarani (Tapurian)

• **Parthian (extinct)

• **Talysh

• **Deilami

• **Zazaki

• *Southwestern ("Persid")

• **Old Persian (extinct)

• ***Middle Persian (extinct)

• ****New Persian (eastern & western dialects)

• ***** Tajik Persian

• ***Luri / Bakhtiari

• ***Tati

Indo-Aryan Group:

• Vedic Sanskrit

• Sanskrit

• Pāli

• Central Zone

• *Hindustani

• **Hindi

• **Urdu

• *Romani/Romany

• Eastern Zone (Magadhan Prakrit languages)

• *Angika

• *Assamese

• *Bengali

• *Bhojpuri

• *Magahi

• *Maithili

• *Oriya

• Northern Zone (Pahari languages)

• *Nepali

• Northwestern Zone

• *Dardic languages (sometimes still classified separately):

• **Dameli

• **Domaaki

• **Gawar-Bati

• **Kalasha-mun

• **Kashmiri

• **Khowar

• **Kohistani

• **Ningalami

• **Pashayi

• **Palula

• **Shina

• **Shumashti

• *Punjabi

• *Sindhi

• *Khojki

• *Kutchi

• *Rajasthani

• Southern Zone (also known as Insular Indo-Aryan)

• *Dhivehi / Mahl

• *Sinhala

• Western Zone

• *Gujarati

• *Konkani

• *Marathi

Nuristani languages:

• Ashkunu (Ashkun)

• Kamkata-viri (Bashgali)

• Vasi-vari (Prasuni)

• Tregami

• Kalasha-ala (Waigali)