Gautama Buddha or (Pali) Gotama Buddha (also the Historical Buddha; Siddhartha Gautama or (Pali) Siddhattha Gotama; Shakyamuni or (Pali) Sakkamuni; and (the) Buddha) was an ascetic and a religious teacher of South Asia who lived in the latter half of the first millennium BCE. He is the founder of Buddhism and revered by Buddhists as an enlightened being whose teachings sought a path to freedom from ignorance, craving, rebirth and suffering. Born in Lumbini in what is today Nepal in the clan of Shakya, he spent the majority of his adult life in what is today India, attaining enlightment in Bodhgaya, preaching his first sermon on the Four Noble Truths in Sarnath, where also the Buddhist sangha or community came to life, and attaining death in the form of Nirvana in Kushinagar.

The Buddha was born into an aristocratic family in the Shakya clan, but eventually renounced lay life. According to Buddhist tradition, after several years of mendicancy, meditation, and asceticism, he awakened to understand the workings of the cycle of rebirth and how it can be escaped. The Buddha then traveled in the lower Gangetic plain, teaching and building a religious community. The Buddha taught a middle way between sensual indulgence and the severe asceticism found in the Indian srama?a movement. He taught a training of the mind that included ethical training, self-restraint, and meditative practices such as jhana and mindfulness. The Buddha also critiqued the practices of Brahmin priests, such as animal sacrifice and the caste system.

A couple of centuries after his death he came to be known by the title Buddha, which means "Awakened One" or "Enlightened One". Gautama's teachings were compiled by the Buddhist community in the Vinaya, his codes for monastic practice, and the Suttas, texts based on his discourses. These were passed down in Middle Indo-Aryan dialects through an oral tradition. Later generations composed additional texts, such as systematic treatises known as Abhidharma, biographies of the Buddha, collections of stories about the Buddha's past lives known as Jataka tales, and additional discourses, i.e. the Mahayana sutras.

Many Hindus claim that Buddha was Hindu and cite a belief that the Buddha is the ninth avatar of Vishnu in support. The adoption of the Buddha as an incarnation began at approximately the same time as Hinduism began to predominate and Buddhism to decline in India, the co-option into a list of avatars seen to be an aspect of Hindu efforts to decisively weaken Buddhist power and appeal in India.