Hinduism is a Dharmic or Indic religion widely practiced in South Asia. It is characterized by being made up of different Hindu religious denominations. If considered a single religion, Hinduism would then be the oldest religion in history and the third largest religion in the world, with about 1.2 billion followers, or 15% of the world's population, known by the generic name of "Hindus."​

The word "Hindu" is based on the exonym (i.e. the foreign name for a toponym) Sindhu, which is the name the Persians gave to the Indus River, which formed the border between Persia and Hindustan.6​7​
According to believers in these doctrines, it is the oldest religion in the world (Sanātana dharma or Sanatana dharma (सनातन धर्म), which literally means "eternal religion"). The term is understood as the condensation into a single spiritual tradition of Brahmanism, Vedism, and Proto-Indo-European and Proto-Indo-Iranian religion. 8​9​10​11​
An incorrect endonym is vaidika dharma,12​13​14​15​16​ ('Vedic religion'), because Vedism was an earlier religion with which Hinduism has many theological differences.17​It is also referred to locally as Hindu Dharma (Hindi: हिन्दू धर्म).

Scholars regard Hinduism as a fusion or synthesis of various Indian cultures and traditions, with diverse roots and without any single founder. Hinduism is a diverse system of thought marked by a number of shared doctrines and concepts, rituals, cosmological systems, pilgrimage sites, and shared textual sources dealing with theology, metaphysics, mythology, Vedic yagña, yoga, agamic rituals, and temple building, among other topics.
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Prominent themes in Hindu beliefs include the four puruṣārthas, the goals or objectives of human life, namely: dharma (ethics/duties), artha (prosperity/work), kāma (desires/passions), and mokṣa (liberation/freedom from passions and the cycle of death and rebirth), as well as karma (action, intention, and consequences) and saṃsāra (cycle of death and rebirth).21​22​ Hinduism prescribes eternal duties, such as honesty, refraining from harming living beings (ahiṃsā), patience, self-control, virtue, and compassion, among others.

Hindu practices include worship (puja), fire rituals (joma/javan), recitations (pravachan), devotion (bhakti), chanting (yapa), meditation (dhyāna), sacrifice (yajña), charity (dāna), selfless service (sevā), homage to ancestors (śrāddha), family-oriented rites of passage, annual festivals, and occasional pilgrimages (yatra).

Along with practicing various yogas, some Hindus abandon their social world and material possessions and dedicate themselves to lifelong sannyasa (monasticism) to attain mokṣa.