The Aitareya Upanishad is one of the older, "primary" Upanishads commented upon by acharyas such as Adi Shankara and Madhvacharya. It is a Mukhya Upanishad, associated with the Rigveda. It figures as number 8 in the Muktika canon of 108 Upanishads.
The Aitareya Upanishad is a short prose text, divided into three chapters, containing 33 verses. It comprises the fourth, fifth and sixth chapters of the second book of the older vedic text, Aitareya Aranyaka.
The rishi of the Aitareya Aranyaka and the Aitareya Brahmana is Aitareya Mahidasa. In Chandogya Upanishad, Aitareya Mahidasa is said to have lived for 116 years (Chhandogya 3.16.7).
In the first chapter of the text, Atman, the inner self, is portrayed as a divine creator. In the second chapter, the three births of the Atman are described. The third chapter deals with the qualities of the self or Brahman. It contains one of the most famous expressions of the Vedanta, "Prajnanam Brahma", which is one of the Mahāvākyas.
The first written English translation was published in 1805 by Colebrooke.