Swami Vivekananda, born Narendranath Datta, was an Indian Hindu monk, a chief disciple of the 19th-century Indian mystic Ramakrishna. He was a key figure in the introduction of the Indian philosophies of Vedanta and Yoga to the Western world and is credited with raising interfaith awareness, bringing Hinduism to the status of a major world religion during the late 19th century. He was a major force in the revival of Hinduism in India, and contributed to the concept of Indian nationalism as a tool of fight against the British empire in colonial India. Vivekananda founded the Ramakrishna Math and the Ramakrishna Mission. He is perhaps best known for his speech which began with the words - "Sisters and brothers of America ...," in which he introduced Hinduism at the Parliament of the World's Religions in Chicago in 1893.

Vivekananda was born Narendranath Datta (shortened to Narendra or Naren) in a Bengali family[13][14] at his ancestral home at 3 Gourmohan Mukherjee Street in Calcutta,[15] the capital of British India, on 12 January 1863 during the Makar Sankranti festival. He belonged to a traditional family and was one of nine siblings. His father, Vishwanath Datta, was an attorney at the Calcutta High Court. Durgacharan Datta, Narendra's grandfather was a Sanskrit and Persian scholar who left his family and became a monk at age twenty-five. His mother, Bhubaneswari Devi, was a devout housewife. The progressive, rational attitude of Narendra's father and the religious temperament of his mother helped shape his thinking and personality.

Narendranath was interested in spirituality from a young age and used to meditate before the images of deities such as Shiva, Rama, Sita, and Mahavir Hanuman. He was fascinated by wandering ascetics and monks. Naren was naughty and restless as a child, and his parents often had difficulty controlling him. His mother said, "I prayed to Shiva for a son and he has sent me one of his demons"

In 1881 Narendra first met Ramakrishna, who became his spiritual focus after his own father had died in 1884. Narendra's first introduction to Ramakrishna occurred in a literature class at General Assembly's Institution when he heard Professor William Hastie lecturing on William Wordsworth's poem, The Excursion. While explaining the word "trance" in the poem, Hastie suggested that his students visit Ramakrishna of Dakshineswar to understand the true meaning of trance. This prompted some of his students (including Narendra) to visit Ramakrishna. They probably first met personally in November 1881, though Narendra did not consider this their first meeting, and neither man mentioned this meeting later. At this time Narendra was preparing for his upcoming F. A. examination, when Ram Chandra Datta accompanied him to Surendra Nath Mitra's, house where Ramakrishna was invited to deliver a lecture. According to Paranjape, at this meeting Ramakrishna asked young Narendra to sing. Impressed by his singing talent, he asked Narendra to come to Dakshineshwar.

In late 1881 or early 1882, Narendra went to Dakshineswar with two friends and met Ramakrishna. This meeting proved to be a turning point in his life. Although he did not initially accept Ramakrishna as his teacher and rebelled against his ideas, he was attracted by his personality and began to frequently visit him at Dakshineswar. He initially saw Ramakrishna's ecstasies and visions as "mere figments of imagination" and "hallucinations". As a member of Brahmo Samaj, he opposed idol worship, polytheism and Ramakrishna's worship of Kali. He even rejected the Advaita Vedanta of "identity with the absolute" as blasphemy and madness, and often ridiculed the idea. Narendra tested Ramakrishna, who faced his arguments patiently: "Try to see the truth from all angles", he replied. Narendra's father's sudden death in 1884 left the family bankrupt; creditors began demanding the repayment of loans, and relatives threatened to evict the family from their ancestral home. Narendra, once a son of a well-to-do family, became one of the poorest students in his college. He unsuccessfully tried to find work and questioned God's existence, but found solace in Ramakrishna and his visits to Dakshineswar increased.