Dattatreya Upanishad is one of the 32 Upanishads in Atharvaveda. Here you can download Dattatreya Upanishad PDF document for free in Sanskrit.
It is a conversation between Lord Vishnu and Lord Brahma about the Dattatreya thathwam.
The Dattatreya Upanishad explains about the Anushtubh mantra of Dattatreya and Moola Mantra of Dattatreya.
Lord Dattatreya is known as the avatar of Trimurthi – Lord Shiva, Vishnu, and Brahma. He is the son of Sage Atri and Anasuya.