The Udasis were key interpreters of the Sikh philosophy and the custodians of important Sikh shrines until the Akali movement. They brought a large number of people in the Sikh fold during the 18th and the early 19th centuries. However, their religious practicies border on a syncretism of Sikhism and Hinduism. When the Singh Sabha, dominated by Khalsa Sikhs, redefined the Sikh identity in the early 20th century, the Udasi mahants were expelled from the Sikh shrines. Since then, the Udasis have increasingly regarded themselves as Hindus rather than Sikhs.
The word "udasi" is derived from the Sanskrit word udas ("detachment"), and may signify indifference to or renunciation of worldly concerns. Although Nanak emphasized the importance of a social life, his son Sri Chand propagated asceticism and celibacy.
The Udasis gained prominence during the Sikh rule in northern India: before the advent of the Sikh rule, they had around a dozen centres; by the end of Maharaja Ranjit Singh's reign, the number had increased to around 250. The Udasis played an important role in propagating the Sikh philosophy, and during the 18th and the early 19th centuries, their teachings attracted a large number of people to the Sikh fold.
Before the emergence of the Singh Sabha Movement in the late 19th century, they controlled the important Sikh shrines, including the Harimandir Sahib. However, during the Akali movement of the 20th century, the Khalsa Sikhs expelled them from the Sikh shrines, accusing them of vices and of indulging in ritual practicies that were against the teachings of the Sikh gurus. The Sikh Gurdwara Reform Act, 1925 defined the term "Sikh" in a way that excluded the syncretist groups like the Udasis, the Nanakpanthis and Sanatanis. Subsequently, the Udasis increasingly identified themselves as Hindus rather than Sikhs.
The Udasis do not reject the Sikh Gurus, but attach greater importance to the line of succession from Guru Nanak through Sri Chand to the Udasi mahants. They interpret the message of Guru Granth Sahib in Vedantic terms. They do not abide by the Khalsa's Rehat Maryada.
Traditionally, there were four Udasi centres (akharas or dhuans) with each controlling a certain preaching area; Nanakmatta, Kashmir, Malwa (Punjab) and Doaba. There is an Udasi gurudwara (temple) in Amritsar, near the Harimandir Sahib (Golden Temple).
- Niya (New) Udasi Panchayati Akarda
- Bara (Big) Udasi Panchayati Akarda
- Nirmal Udasi Panachayati Akarda
- Pashaura Singh; Louis E. Fenech (2014). The Oxford Handbook of Sikh Studies. OUP Oxford. pp. 375–376. ISBN 978-0-19-100412-4.
- Tanweer Fazal (1 August 2014). "Nation-state" and Minority Rights in India: Comparative Perspectives on Muslim and Sikh Identities. Routledge. p. 113. ISBN 978-1-317-75179-3.
- John Stratton Hawley; Gurinder Singh Mann (1993). Studying the Sikhs: Issues for North America. SUNY Press. p. 182. ISBN 978-0-7914-1426-2.
- David N. Lorenzen (1995). Bhakti Religion in North India: Community Identity and Political Action. SUNY Press. p. 57. ISBN 978-0-7914-2025-6.
- J. S. Grewal (1998). The Sikhs of the Punjab. Cambridge University Press. p. 116. ISBN 978-0-521-63764-0.
- James G. Lochtefeld (2002). The Illustrated Encyclopedia of Hinduism: A-M. The Rosen Publishing Group. p. 61. ISBN 978-0-8239-3179-8.