Dattatreya is the God who is an incarnation of the Divine Trinity Brahma, Vishnu and Shiva. The word Datta means "Given", Datta is called so because the divine trinity have "given" themselves in the form of a son to the sage couple Guru Atri and Mata Anusuya. He is the son of Guru Atri, hence the name "Atreya."
In the Nath tradition, Dattatreya is seen as an Avatar or incarnation of the Lord Shiva and as the Adi-Guru (First Teacher) of the Adi-Nath sampradaya of the Nathas. Although Dattatreya was at first a "Lord of Yoga" with Tantric traits, he was adapted into the more devotional cults; while still worshiped by millions of Hindus, he is approached more as a benevolent God than as a teacher of the highest essence of Indian thought.