Vaishnavism (Vaishnava dharma) is one of the major traditions within Hinduism along with Shaivism, Shaktism, and Smartism. It is also called Vishnuism, its followers are called Vaishnavas, and it considers Vishnu as the Supreme Lord.

The tradition is notable for its avatar doctrine, wherein Vishnu is revered in one of many distinct incarnations. Of these, ten avatars of Vishnu are the most studied, while Krishna, Rama, Narayana and Vasudeva are the most popular. The tradition has traceable roots to the 1st millennium BCE, as Bhagavatism, also called Krishnaism. Later developments led by Ramananda created a Rama-oriented movement, now the largest monastic group in Asia. The Vaishnava tradition has many sampradayas (denominations, sub-schools) ranging from the medieval era Dvaita school of Madhvacharya to Vishishtadvaita school of Ramanuja. New Vaishnavism movements have been founded in the modern era such as the ISKCON of Prabhupada.

The tradition is known for the loving devotion to an avatar of Vishnu (often Krishna), and it has been key to the spread of Bhakti movement in South Asia in the 2nd millennium CE. Key texts in Vaishnavism include the Vedas, the Upanishads, the Bhagavad Gita, the Pancaratra (Agama) texts and the Bhagavata Purana. Within Hinduism an estimated 640 million or 67.6% followers are Vaishnavas.

Vaishnavas often identify six qualities of God: all knowledge, all power, supreme majesty, supreme strength, unlimited energy and total self-sufficiency. One popular name for God among Vaishnavites is an ancient name from the Vedas: Purushottama, "the Supreme Person." For most Vaishnavas, the divine Self within is Vishnu himself, but not all of Vishnu. In other words, Vishnu is more than the Self and more than the universe. Likewise, when a Vaishnavite merges into God upon liberation, his or her individual nature is not lost. Vaishnavites believe people are meant to be God's companions for all eternity.