The Brahmo Samaj was founded in Calcutta in 1828 by Ram Mohan Roy, a Bengali scholar fluent in Sanskrit, Persian, Arabic and English, who had studied the Upanishads, the Quran and the Christian gospels closely. Roy argued that the Upanishads taught a single formless God, and that image worship, caste restriction and later ritual accretions had obscured this original monotheism. The Samaj he founded held regular prayer meetings built around Sanskrit and Bengali readings, congregational worship without images, and hymns, borrowing the outward form of Protestant worship while insisting its content was authentically Hindu and Vedantic.
Roy's reform activity extended beyond religious organization: he campaigned publicly against sati, the practice of widow immolation, and pressed British colonial authorities to outlaw it, which they did in 1829, the year after the Samaj's founding. He also promoted English and scientific education alongside Sanskrit learning, arguing that Indian society needed both to reform itself.
After Roy's death in 1833, the Brahmo Samaj continued under new leadership, most notably Debendranath Tagore, who gave the movement a more systematic theological basis grounded in the Upanishads, and later Keshub Chandra Sen, whose more radical universalism led to a formal split in 1866. Despite these divisions, the Samaj's influence on nineteenth century Indian religious and social reform, particularly in Bengal, was considerable.