Siddhārtha Gautama (Sanskrit: सिद्धार्थ गौतम; Pali:सिद्धाथ गोतम Siddhattha Gotama) was a spiritual teacher from ancient India who founded Buddhism. In most Buddhist traditions, he is regarded as the Supreme Buddha (P. sammāsambuddha, S. samyaksaṃbuddha ) of our age, "Buddha" meaning "awakened one" or "the enlightened one." The time of his birth and death are uncertain: most early 20th-century historians dated his lifetime as c. 563 BCE to 483 BCE; more recently, however, at a specialist symposium on this question, the majority of those scholars who presented definite opinions gave dates within 20 years either side of 400 BCE for the Buddha's death, with others supporting earlier or later dates.

Gautama, also known as Śākyamuni or Shakyamuni ("sage of the Shakyas"), is the key figure in Buddhism, and accounts of his life, discourses, and monastic rules are believed by Buddhists to have been summarized after his death and memorized by his followers. Various collections of teachings attributed to Gautama were passed down by oral tradition, and first committed to writing about 400 years later.

He is also a minor figure in other religions: in some Hindu texts, he is described as an avatar of god Vishnu who attempted to delude beings away from the Vedic religion, and he is regarded as a prophet in the Bahá'í faith.