Aryan or Arya is a term originally used as an ethnocultural self-designation by Indo-Iranians in ancient times, in contrast to the nearby outsiders known as 'non-Aryan'. In Ancient India, the term ā́rya was used by the Indo-Aryan speakers of the Vedic period as an endonym (self-designation) and in reference to a region known as Āryāvarta, where the Indo-Aryan culture emerged. In the Avesta scriptures, ancient Iranian peoples similarly used the term airya to designate themselves as an ethnic group, and in reference to their mythical homeland, Airyanǝm Vaēǰō. The stem also forms the etymological source of place names such as Alania and Iran.

Houston Stewart Chamberlain was a British-German philosopher who wrote works about political philosophy and natural science. His writing promoted German ethnonationalism, antisemitism, scientific racism, and Nordicism; he has been described as a "racialist writer". His best-known book, the two-volume Die Grundlagen des neunzehnten Jahrhunderts, published 1899, became highly influential in the pan-Germanic Völkisch movements of the early 20th century, and later influenced the antisemitism of Nazi racial policy. Indeed, Chamberlain has been referred to as "Hitler's John the Baptist".