Indo-Iranian peoples are a linguistic group consisting of the Indo-Aryan, Iranian, Dardic and Nuristani peoples; that is, speakers of Indo-Iranian languages, a major branch of the Indo-European language family.

The Proto-Indo-Iranians are commonly identified with the descendants of the Proto-Indo-Europeans known as the Andronovo culture and their homeland with an area of the Eurasian steppe that borders the Ural River on the west, the Tian Shan on the east.

The term Aryan has generally been used historically to denote the Indo-Iranians because Arya is the self designation of the Indo-Iranian languages and their speakers, specifically the Iranian and the Indo-Aryan peoples, collectively known as the Indo-Iranians. Some scholars now use the term Indo-Iranian to refer to this group, while the term "Aryan" is used to mean "Indo-Iranian" by other scholars such as Josef Wiesehofer.Population geneticist Luigi Luca Cavalli-Sforza, in his 1994 book The History and Geography of Human Genes, also uses the term Aryan to describe the Indo-Iranians.

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 Indo-Iranian languages occasionally go by the term "Aryan languages." The speakers of the Proto-Indo-Iranian language, the hypothetical Proto-Indo-Iranians, are usually associated with the late 3rd millennium BC Andronovo and Sintashta-Petrovka cultures 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) eastward to Xinjiang (Sarikoli) and Assam (Assamese) and south to Sri Lanka (Sinhalese). SIL in a 2005 estimate counts a total of 308 varieties, the largest in terms of native speakers being Hindustani (Hindi and Urdu, ca. 190-330 million), Bengali (ca. 190 million), Punjabi (ca. 88 million), Marathi (ca. 70 million), Persian (ca. 70 million), Pashto (ca. 50 million), Gujarati (ca. 46 million), Kurdish (ca. 16-30 million), Bhojpuri (ca. 35 million), Awadhi (ca. 35 million), Maithili (ca. 35 million), Oriya (ca. 32 million), Marwari (ca. 31 million), Sindhi (ca. 21 million), Rajasthani (ca. 20 million), Chhattisgarhi (ca. 17 million), Assamese (ca. 17 million), Sinhalese (ca. 16 million), and Rangpuri (ca. 15 million).

The Kurdish people, or Kurds (Kurdish: کورد Kurd), are an Iranic people native to the Middle East, mostly inhabiting a region known as Kurdistan, which includes adjacent parts of Iran, Iraq, Syria, and Turkey. They speak the Kurdish language, which is a member of the Iranian branch of Indo-European languages. The Kurds number about 30 million, the majority living in the Middle East, with significant Kurdish diaspora communities in the cities of western Turkey, in Armenia, Georgia, Israel, Azerbaijan, Russia, Lebanon and, in recent decades, some European countries and the United States. The Kurds are an indigenous ethnic minority in countries where the Kurdistan region is located, although they have enjoyed partial autonomy in Iraqi Kurdistan since 1991. An irredentist movement pushes for the creation of a Kurdish nation state.

The exact origins of the name, "Kurd", are unclear. Reynolds believes that the term Kurd is most likely related to the ancient term Qardu. The common root of Kurd and Qardu is first mentioned in a Sumerian tablet from the third millennium B.C. as the "land of Kar-da." Qardu is etymologically related to the Assyrian term Urartu corresponding to Ararat. According to Asatrian, the most reasonable explanation of this ethnonym is its possible connections with the Cyrtii (Cyrtaei)

Tajik (Persian: تاجيک‎, Tājīk; Tajik: Тоҷик) is a general designation for a wide range of Persian-speaking people of Iranic origin, with traditional homelands in present-day Afghanistan, Tajikistan, and Uzbekistan. There are also smaller communities living in Iran and Pakistan; consisting mainly of refugees from Afghanistan and immigrants from Tajikistan.

In terms of language, culture, and history the Tajiks are closely related to the Persians of Iran.

As a self-designation, the term Tajik, which earlier on had been more or less pejorative, has become acceptable only during the last several decades, particularly as a result of Soviet administration in Central Asia. Alternative names for the Tajiks are Fārsī (Persian), Fārsīwān (Persian-speaker), and Dīhgān (cf. Tajik: Деҳқон, Dehqon, literally "farmer or settled villager", in a wider sense "settled" in contrast to "nomadic").

The Tajiks of China, although known by the name Tajik, speak Eastern Iranian languages and are distinct from Persian Tajiks.