Aryan (/ˈɛəriən/), or Arya (borrowed from Sanskrit ārya), is a term originating from the ethno-cultural self-designation of the Indo-Iranians. It stood in contrast to nearby outsiders, whom they designated as non-Aryan (*an-āryā). In ancient India, the term was used by the Indo-Aryan peoples of the Vedic period, both as an endonym and in reference to a region called Aryavarta (lit. 'Land of the Aryans'), where their culture emerged. Similarly, according to the Avesta, the Iranian peoples used the term to designate themselves as an ethnic group and to refer to a region called Airyanem Vaejah (lit. 'Expanse of the Arya'), which was their mythical homeland. The word stem also forms the etymological source of place names like Alania (*Aryāna) and Iran (*Aryānām).

Although the stem *arya may originate from the Proto-Indo-European language, it seems to have been used exclusively by the Indo-Iranian peoples, as there is no evidence of it having served as an ethnonym for the Proto-Indo-Europeans. The view of many modern scholars is that the ethos of the ancient Aryan identity, as it is described in the Avesta and the Rigveda, was religious, cultural, and linguistic, and was not tied to the concept of race.

In the 1850s, the French diplomat and writer Arthur de Gobineau brought forth the idea of the "Aryan race", essentially claiming that the Proto-Indo-Europeans were superior specimens of humans and that their descendants comprised either a distinct racial group or a distinct sub-group of the hypothetical Caucasian race. Through the work of his later followers, such as the British-German philosopher Houston Stewart Chamberlain, Gobineau's theory proved to be particularly popular among European racial supremacists and ultimately laid the foundation for Nazi racial theories, which also co-opted the concept of scientific racism.

In Nazi Germany, and also in German-occupied Europe during World War II, any citizen who was classified as an Aryan would be honoured as a member of the "master race" of humanity. Conversely, non-Aryans were legally discriminated against, including Jews, Roma, and Slavs (mostly Poles and Russians). Jews, who were regarded as the arch enemy of the "Aryan race" in a "racial struggle for existence", were especially targeted by the Nazi Party, culminating in the Holocaust. The Roma, who are of Indo-Aryan origin, were also targeted, culminating in the Porajmos. The genocides and other large-scale atrocities that have been committed by Aryanists have led academic figures to generally avoid using "Aryan" as a stand-alone ethno-linguistic term, particularly in the Western world, where "Indo-Iranian" is the preferred alternative, although the term "Indo-Aryan" is still used to denote the Indic branch.

The term Arya was first rendered into a modern European language in 1771 as Aryens by French Indologist Abraham-Hyacinthe Anquetil-Duperron, who rightly compared the Greek arioi with the Avestan airya and the country name Iran. In Germany, Johann Friedrich Kleuker's translation of Anquetil-Duperron's work led to the introduction of the term Arier in 1776.

The Sanskrit word ā́rya is rendered as 'noble' in William Jones' 1794 translation of the Indian Laws of Manu. The English Aryan (originally spelt Arian) appeared a few decades later, first as an adjective in 1839, then as a noun in 1849, probably after the German Arier (noun), arisch (adjective). During the 19th and early 20th centuries, the meaning varied between the broader category equivalent to Indo-European, and the narrower one equivalent to Indo-Iranian.

Use of Aryan to designate a "white non-Jewish person, especially one of northern European origin or descent" entered the English language from German, after this meaning was introduced in 1887 and further developed by German anti-Semitic propagandists in the context of a so-called "Aryan race". It is still used in far-right and white supremacist discourse, and sometimes appears in the names of such groups.

The Sanskrit word ā́rya (आर्य) was originally an ethnocultural term designating those who spoke Vedic Sanskrit and adhered to Vedic cultural norms (including religious rituals and poetry), in contrast to an outsider, or an-ā́rya ('non-Arya'). By the time of the Buddha (5th–4th century BCE), it took the meaning of 'noble'. In Old Iranian languages, the Avestan term airya (Old Persian ariya) was likewise used as an ethnocultural self-designation by ancient Iranian peoples, in contrast to an an-airya ('non-Arya'). It designated those who belonged to the 'Aryan' (Iranian) ethnic stock, spoke the language and followed the religion of the 'Aryas'.