Married by arrangement at 13, Gandhi went to London to study law when he was 18. He was admitted to the bar in 1891 and for a while practiced law in Bombay. From 1893 to 1914 he worked for an Indian firm in South Africa. During these years Gandhi's humiliating experiences of overt racial discrimination propelled him into agitation on behalf of the Indian community of South Africa. He assumed leadership of protest campaigns and gradually developed his techniques and tenets of nonviolent resistance known as Satyagraha (literally, "steadfastness in truth").

Returning to India in January 1915, Gandhi soon became involved in labor organizing. The Jallianwala Bagh massacre of Amritsar (1919), in which troops fired on and killed hundreds of nationalist demonstrators, turned him to direct political protest. Within a year he was the dominant figure in the Indian National Congress, which he launched on a policy of noncooperation with the British in 1920-22. Although total noncooperation was abandoned, Gandhi continued civil disobedience, organizing protest marches against unpopular British measures, such as the salt tax (1930), and boycotts of British goods.

Gandhi was repeatedly imprisoned by the British and resorted to hunger strikes as part of his civil disobedience. His final imprisonment came in 1942-44, after he had demanded total withdrawal of the British (the "Quit India" movement) during World War II.

Gandhi also fought to improve the status of the lowest classes of society, the ‘Untouchables’, whom he called harijans ("children of God"). He believed in manual labor and simple living; he spun thread and wove cloth for his own garments and insisted that his followers do so, too. He disagreed with those who wanted India to industrialize.

Gandhi was also tireless in trying to forge closer bonds between the Hindu majority and the numerous minorities of India, particularly the Muslims. His greatest failure, in fact, was his inability to dissuade Indian Muslims, led by Muhammad Ali Jinnah, from creating a separate state, Pakistan. When India gained independence in 1947, after negotiations in which he was a principal participant, Gandhi opposed the partition of the subcontinent with such intensity that he launched a mass movement against it. Ironically, he was assassinated in Delhi on January 30, 1948, by a Hindu fanatic who mistakenly thought Gandhi's anti-partition sentiment were both pro-Muslim and pro-Pakistan.