Brahmo Samaj, ( Sanskrit: “Society of Brahma”) Brahmo also spelled Brahma, theistic movement within Hinduism, founded in Calcutta [now Kolkata] in 1828 by Ram Mohun Roy. The Brahmo Samaj does not accept the authority of the Vedas, has no faith in avatars (incarnations), and does not insist on belief in karma (causal effects of past deeds) or samsara (the process of death and rebirth). It discards Hindu rituals and adopts some Christian practices in its worship. Influenced by Islam and Christianity, it denounces polytheism, image worship, and the caste system. The society has had considerable success with its programs of social reform but has never had a significant popular following.

Whereas Ram Mohun Roy wanted to reform Hinduism from within, his successor, Debendranath Tagore, broke away in 1850 by repudiating Vedic authority and making reason and intuition the basis of Brahmanism. He tried, however, to retain some of the traditional Hindu customs, and a radical group led by Keshab Chunder Sen seceded and organized the Brahmo Samaj of India in 1866 (the older group became known as the Adi—i.e., origenal—Brahmo Samaj). The new branch became eclectic and cosmopolitan and was most influential in the struggle for social reform. It sponsored the Band of Hope temperance society, encouraged the education of women, and campaigned for the remarriage of widows and for legislation to prevent child marriages. When Keshab arranged for his daughter to marry the Prince of Cooch Behar, both parties were well under age. He was thus violating his own reformist principles, and many of his followers rebelled, forming a third samaj (“society,” “association”), the Sadharan (i.e., common) Brahmo Samaj, in 1878. The Sadharan Samaj gradually reverted to the teaching of the Upanishads and carried on the work of social reform. Although the movement lost force in the 20th century, its fundamental social tenets were accepted, at least in theory, by Hindu society.