Udasis (Gurmukhi: ਉਦਾਸੀ ਸੰਪਰਦਾ; udāsī saparadā), also spelt as Udasins, also known as Nanak Putras (meaning "sons of Nanak"), are a religious sect of ascetic sadhus centred in northern India who follow a tradition known as Udasipanth. Becoming custodians of Sikh shrines in the 18th century, they were notable interpreters and spreaders of the Sikh philosophy during that time. However, their religious practices border on a syncretism of Sikhism and Hinduism, including idolatry, and they did not conform to the Khalsa standards as ordained by Guru Gobind Singh. When the Lahore Singh Sabha reformers, dominated by Tat Khalsa Sikhs, would hold them responsible for indulging in ritual practices antithetical to Sikhism, as well as personal vices and corruption, the Udasi mahants were expelled from the Sikh shrines.
Udasi and Udasin is derived from the Sanskrit word Udāsīn, which means one who is indifferent to or disregardful of worldly attachments, a stoic, or a mendicant. The word Udasi is derived from the Sanskrit word udasin, meaning 'detached, journey', reflecting an approach to spiritual and temporal life, or from udas ('detachment'), signifying indifference to or renunciation of worldly concerns.
According to myth, the sect was established in the Puranic age but historically speaking, the sect was founded by and based on the teachings of Guru Nanak's elder son Sri Chand (1494–1629, other sources give a death year of 1643). Sri Chand, contrary to his father's emphasis on participation in society, propagated ascetic renunciation and celibacy. Another Sikh tradition links the Udasis to Baba Gurditta, the eldest son of Guru Hargobind, and there is dispute on whether the Udasis originated with Sri Chand or Gurditta. Another viewpoint is that Sri Chand was the founder of the sect and passed the leadership to Baba Gurditta as his successor.
They maintain their own parallel line of gurus from Guru Nanak, followed by Sri Chand, followed by Gurditta.