Dhanvantari is the physician of the gods and the presiding deity of Ayurveda, the classical Indian system of medicine. He rises from the churning of the ocean of milk (samudra manthana) holding the pot of amrita, the nectar that ends death, and is counted an avatar of Vishnu; he is shown four-armed, carrying a conch, a discus, a leech and the pot of nectar.
The Sushruta Samhita, one of the two foundational texts of Ayurvedic medicine and surgery, presents its teaching as descending from him. Many practitioners today invoke Dhanvantari at the start of treatment and of study, and Dhanteras, the first day of Diwali, is kept as his day; the Government of India designated it National Ayurveda Day in 2016, and in 2024 moved the observance to a fixed calendar date, a sign of the deity's continuing institutional presence in a living medical tradition. The Sushruta Samhita's own dating is contested.
Tradition places Sushruta himself around the sixth century BCE, but the text as it survives shows signs of substantial later reworking, most importantly a redaction traditionally attributed to a physician named Nagarjuna, whom the medieval commentator Dalhana credits with adding the Uttara Tantra section; specialists differ on whether that redaction belongs to the last centuries BCE or as late as the third or fourth century CE, so the surviving Sushruta Samhita is best understood as a layered text rather than a single-author work fixed at one date, with Dhanvantari's authorship remaining a traditional attribution of authority rather than a claim about a historical composer.