the religion of the ancient Indo-European-speaking peoples who entered India about 1500 BC from the region of present-day Iran; it takes its name from the collections of sacred texts known as the Vedas. Vedism is the oldest stratum of religious activity in India for which there exist written materials. It was the starting point of Hinduism.

Knowledge of Vedic religion is derived from surviving texts and also from certain rites that continue to be observed within the framework of modern Hinduism. The earliest Vedic religious beliefs included some held in common with other Indo-European-speaking peoples, particularly with the early Iranians. Though it is impossible to say when Vedism eventually gave way to classical Hinduism, a decrease in literary activity among the Vedic schools from the 5th century BC onward can be observed, and about this time texts of Hindu character began to appear.

The only extant Vedic materials are the texts known as the Vedas, which were written down over a period of about 10 centuries, from about the 15th to the 5th century BC, this being the period when Vedism was a living force. The Vedic corpus is written in an archaic Sanskrit. The most important texts are also the oldest ones. They are the four collections (Samhita) that we call the Veda, or Vedas. The Rigveda, or “Veda of Verses,” the earliest of these, is composed of about 1,000 hymns addressed to various deities, and mostly arranged to serve the needs of the priestly families who were the custodians of this sacred literature. The Yajurveda, or “Veda of Sacrificial Formulas,” contains prose formulas applicable to various cultic rites, along with verses intended for a similar purpose. The Samaveda, or “Veda of Chants” is made up of a selection of verses (drawn almost wholly from the Rigveda) that are provided with musical notation and are intended as an aid to the performance of sacred songs. Finally, the Atharvaveda is considered to be either of less worth than or of similar content to the three earlier collections.

To each Veda is attached a body of prose writings of later date called Brahmanas (Brāhmaṇa) (c. 800–600 BC), which are intended to explain the ceremonial applications of the texts and the origin and importance of the sacrificial rites for which the Vedas were supposed to have been composed. Further appendices, the Aranyakas (Āraṇyakas) (c. 600 BC) and the Upanishads (Upanishad) (c. 700–500 BC), respectively expound the symbolism of the more difficult rites and speculate on the nature of the universe and man's relation to it.

When Vedic religion gradually evolved into Hinduism between the 6th and 2nd centuries BC, these texts taken collectively became the most sacred literature of Hinduism. They are known as Sruti (Śruti), or the divinely revealed section of Hindu literature, in contrast to the later strata of religious literature known as Smriti (Smṛti), or traditional texts based on human memory. But in modern Hinduism the Sruti, with the exception of the Upanishads and a few hymns of the Rigveda, is now little known, while some of the Smriti texts, notably the Bhagavadgita, are extremely influential.

Vedism was a polytheistic sacrificial religion that was very different from its successor, Hinduism. Vedism involved the worship of numerous male divinities who were connected with the sky and natural phenomena. The priests who officiated at this worship were known as Brahmans. The complex Vedic ceremonies, for which the hymns of the Rigveda were composed, centred on the ritual sacrifice of animals and with the pressing and drinking of a sacred intoxicating liquor called soma. The basic Vedic rite was performed by offering these edibles to a sacred fire, and this fire, which was itself deified as Agni, carried the oblations to the gods of the Vedic pantheon. The greatest deities of Vedism were at the same time material elements of the ritual offering: on the one hand, Agni (i.e., fire), which was equally the fire of the sun, of lightning, of burning wood, and of that which made light for the purpose of religious worship; and on the other hand, Soma, which was simply the deified aspect of the liquid poured in the oblation. The god of highest rank, however, was Indra, a warlike god who conquered innumerable human and demon enemies and vanquished the sun, among other epic feats. Another great deity was Varuna (Varuṇa), who was the upholder of the cosmic and moral laws. Vedism had many other lesser deities, among whom were gods, demigods, and demons.

The ancient Vedic worshipers offered sacrifices to these gods in the hope that they in return would grant abundant numbers of cattle, good fortune, good health, long life, and male progeny, among other material benefits. To ensure the efficacy of their prayers, the people came to believe that their offerings could be made more acceptable to the gods if accompanied by songs of praise and other invocations of the gods' might and power. Thus originated the rites described in the Vedas. Every sacrifice was performed on behalf of an individual, the yajamana (“sacrificer”), who bore the expenses.

The rites of Vedic sacrifice were relatively simple in the early period, when the Rigveda was written down. They required neither temples nor images; the ceremonies took place in an open space that was consecrated afresh for every important occasion. The altar (vedi) was a quadrangle marked out by hollowing or slightly raising the ground. The agnyadheya (“installation of the fire”) was a necessary preliminary to all the large public rituals and was preceded by the patron's fast. The sacrifices themselves were of two major types—domestic (grihya) and public (srauta, or vaitanika). The domestic rites were observed by the householder himself or with the help of a single priest and were performed over the domestic hearth fire. Some occurred daily or monthly, and others accompanied a particular event, such as the samskaras, sacraments marking each stage of an upper-caste Indian's life, from conception to death. The grand rites performed in public, by contrast, lasted several days or months and could usually be undertaken only by wealthy men or kings. They required the services of many priests and were usually performed at three fire-altars. Most characteristic of the public ceremonies was the soma sacrifice, which ensured the prosperity and well-being of both men and gods. In this basic ritual, a lay sacrificer was first consecrated, after which juice was pressed three times from the soma plant, part being offered to the fire and part consumed by the priests. Each of the three occasions was preceded and followed by recitations and chants. Edibles such as meat, butter, milk, and barley cake could also be offered to a sacred fire. Animal sacrifice—the killing of a ram—existed either independently or as an integral part of the sacrifice of soma. The celebrated ashvamedha (aśvamedha), or “horse-sacrifice,” was an elaborate variant of the soma sacrifice. Human sacrifice (purushamedha) is described and alluded to as a former practice but may have been more symbolic than actual. The sacrifice of the mythical giant Purusha, from whose dismembered limbs sprang up the four major castes, probably served as a model for the conjectured human sacrifices. Other ceremonies marked fixed dates of the lunar calendar, such as the full or new moon or the change of seasons.

Over the centuries, the Vedic rites became increasingly complex and governed by innumerable rules, which were embodied, together with the hymns and prayer formulas used, in the Vedas. During the late Vedic period, the complexities of ritual were emphasized to such an extent that only highly trained Brahmans and priests could carry them out correctly, and it was maintained that if rites were improperly or incorrectly performed, they could, unless rectified, bring about disaster or death.

In reaction against this excessive emphasis on ritual (as well as the growing power of the Brahmans), Vedic thought in its late period became more speculative and philosophical in approach, and more refined and subtle in quality. Much speculation was directed toward the search for harmony and for correspondences between macrocosm and microcosm, with the ultimate goal being a reduction of reality to an all-embracing unity by way of successive equations. In the Aranyakas, Vedic ritual is interpreted in a symbolic rather than a literal manner, and the Upanishads question the very assumptions on which Vedism rested. The crucial idea that emerged from this period of intense questioning was that of brahma, which tended to become a sort of guiding principle, a sort of universal soul, in which the individual soul, or atman, is merged. The equation of atman (the self) with brahma (ultimate reality) became the basis of Hindu metaphysics. The spread in the 6th century BC of the related concepts of the reincarnation of souls, of karma, and of the attainment of release from this cycle by meditation rather than through sacrifice marked the end of the Vedic period and the appearance of Hinduism.

The legacy of Vedic worship is apparent in several aspects of modern Hinduism. The basic stratification of Vedic society into four social classes, or varnas—the Brahmans (priests or teachers), Kshatriya (rulers), Vaishya (traders), and Sudra (non-Aryan serfs)—by and large persisted in later Hinduism. Sacrifices performed according to Vedic rites continue to be performed in India occasionally, and the offering of oblations to a sacred fire (homa) is an important element of much modern Hindu worship (see yajna (yajña)). The Hindu rite of initiation (upanayama) is another direct survival of Vedic tradition. Vishnu and Shiva, the major deities of classical Hinduism, also figured in Vedic mythology, though unimportantly.