Information on the life of Rāmānuja consists only of the accounts given in the legendary biographies about him, in which a pious imagination has embroidered historical details. According to tradition, he was born in southern India, in what is now Tamil Nadu (formerly Madras) state. He showed early signs of theological acumen and was sent to Kāñcī (Kānchipuram) for schooling, under the teacher Yādavaprakāśa, who was a follower of the monistic system of Vedānta of Śaṅkara, the famous 8th-century philosopher. Rāmānuja's profoundly religious nature was soon at odds with a doctrine that offered no room for a personal god. After falling out with his teacher he had a vision of the god Vishnu and his consort Śrī, or Lakṣmī, and instituted a daily worship ritual at the place where he beheld them.

He became a temple priest at the Varadarāja temple at Kāñcī, where he began to expound the doctrine that the goal of those who aspire to final release from transmigration is not the impersonal Brahman but rather Brahman as identified with the personal god Vishnu. In Kāñcī, as well as Śrīraṅgam, where he was to become associated with the Raṅganātha temple, he developed the teaching that the worship of a personal god and the soul's union with him is an essential part of the doctrines of the Upaniṣad (Upanishad)s (ancient speculative texts that are part of Hindu sacred scriptures) on which the system of Vedānta is built; therefore, the teachings of the Vaiṣṇavas and Bhāgavatas (worshippers and ardent devotees of Vishnu) are not heterodox. In this he continued the teachings of Yāmuna (Yāmunācārya; 10th century), his predecessor at Śrīraṅgam, to whom he was related on his mother's side. He set forth this doctrine in his three major commentaries.

Like many Hindu thinkers, he made an extended pilgrimage, circumambulating India from Rāmeswaram (part of Adams Bridge), along the west coast to Badrīnāth, the source of the holy river Ganges, and returning along the east coast. Tradition has it that later he suffered from the zeal of King Kulottuṅga of the Cōla dynasty, who adhered to the god Śiva, and withdrew to Mysore, in the west. There he converted numbers of Jainas (adherents of a dualistic, ascetic sect), as well as King Bittideva of the Hoyṡala dynasty; this led to the founding in 1099 of the town Milukote (Melcote, present Karnataka state) and the dedication of a temple to Śelva Piḷḷai (Sanskrit, Saṃpatkumāra, the name of a form of Vishnu). He returned after 20 years to Śrīraṅgam, where he organized the temple worship, and, reputedly, he founded 74 centres to disseminate his doctrine. After a life of 120 years, according to the tradition, he passed away in 1137.

Rāmānuja's chief contribution to philosophy was his emphasis that discursive thought is necessary in man's search for the ultimate verities, that the phenomenal world is real and provides real knowledge, and that the exigencies of daily life are not detrimental or even contrary to the life of the spirit. In this emphasis he is the antithesis of Śaṅkara, of whom he was sharply critical and whose interpretation of the scriptures he disputed. Like other adherents of the Vedānta system, Rāmānuja accepted that any Vedānta system must base itself on the three “points of departure,” namely, the Upaniṣads, the Brahma-sūtras (brief exposition of the major tenets of the Upaniṣads), and the Bhagavadgītā, the colloquy of the god Kṛṣṇa and his friend Arjuna. He wrote no commentary on any single Upaniṣad but explained in detail the method of understanding the Upaniṣads in his first major work, the Vedārtha-saṃgraha (“Summary of the Meaning of the Veda”). Much of this was incorporated in his commentary on the Brahma-sūtras, the Śrī-bhāṣya, which presents his fully developed views. His commentary on the Bhagavadgītā, the Bhagavadgītā-bhāṣya, dates from a later age.

Although Rāmānuja's contribution to Vedānta thought was highly significant, his influence on the course of Hinduism as a religion has been even greater. By allowing the urge for devotional worship ( bhakti) into his doctrine of salvation, he aligned the popular religion with the pursuits of philosophy and gave bhakti an intellectual basis. Ever since, bhakti has remained the major force in the religions of Hinduism. His emphasis on the necessity of religious worship as a means of salvation continued in a more systematic context the devotional effusions of the Āḷvārs (Āḷvār), the 7th– 10th century poet-mystics of southern India, whose verse became incorporated into temple worship. This bhakti devotionalism, guided by Rāmānuja, made its way into northern India, where its influence on religious thought and practice has been profound.

Rāmānuja's world view accepts the ontological reality of three distinct orders: matter, soul, and God. Like Śaṅkara and earlier Vedānta, he admits that there is nonduality (advaita), an ultimate identity of the three orders, but this nonduality for him is asserted of God, who is modified (viśiṣṭa) by the orders of matter and soul; hence his doctrine is known as Viśiṣṭādvaita (“modified nonduality”) as opposed to the unqualified nonduality of Śaṅkara. Central to his organic conception of the universe is the analogy of body and soul: just as the body modifies the soul, has no separate existence from it, and yet is different from it, just so the orders of matter and soul constitute God's “body,” modifying it, yet having no separate existence from it. The goal of the human soul, therefore, is to serve God just as the body serves the soul. Anything different from God is but a śeṣa of him, a spilling from the plenitude of his being. All the phenomenal world is a manifestation of the glory of God (vibhūti), and to detract from its reality is to detract from his glory. Rāmānuja transformed the practice of ritual action into the practice of divine worship and the way of meditation into a continuous loving pondering of God's qualities; both in turn a subservient to bhakti, the fully realized devotion that finds God. Thus, release is not merely a shedding of the bonds of transmigration but a positive quest for the contemplation of God, who is pictured as enthroned in his heaven, called Vaikuṇṭha, with his consort and attendants.

Rāmānuja's doctrine, which was passed on and augmented by later generations, still identifies a caste of Brahmans in southern India, the Śrīvaiṣṇavas (Śrīvaiṣṇava). They became divided into two subcastes, the northern, or Vaḍakalai, and the southern, or Teṉkalai. At issue between the two schools is the question of God's grace. According to the Vaḍakalai, who in this seem to follow Rāmānuja's intention more closely, God's grace is certainly active in man's quest for him but does not supplant the necessity of man's acting toward God. The Teṉkalai, on the other hand, hold that God's grace is paramount and that the only gesture needed from man is his total submission to God (prapatti).

The site of Rāmānuja's birthplace in Śrīperumbūdūr is now commemorated by a temple and an active Viśiṣṭādvaita school. The doctrines he promulgated still inspire a lively intellectual tradition, and the religious practices he emphasized are still carried on in the two most important Vaiṣṇava centres in southern India, the Raṅganātha temple in Śrīraṅgam, Tamil Nadu, and the Veṅkateśvara temple in Tirupati, Andhra Pradesh.