Waisak is an annual holiday observed traditionally by Buddhists in the Nepal and subcontinent, Sri Lanka, and the South East Asian countries of Singapore, Vietnam, Thailand, Cambodia, Malaysia, Myanmar, and Indonesia.

Waisak or Vesākha is an annual holiday observed traditionally by Buddhists in the Nepal and subcontinent, Sri Lanka, and the South East Asian countries of Singapore, Vietnam, Thailand, Cambodia, Malaysia, Myanmar, and Indonesia. Sometimes informally called "Buddha's Birthday", it actually encompasses the birth, enlightenment (nirvāṇa), and passing away (Parinirvāna) of Gautama Buddha.

Celebrating Vesākha also means making special efforts to bring happiness to the unfortunate like the aged, the handicapped and the sick. To this day, Buddhists will distribute gifts in cash and kind to various charitable homes throughout the country. Vesākha is also a time for great joy and happiness, expressed not by pandering to one’s appetites but by concentrating on useful activities such as decorating and illuminating temples, painting and creating exquisite scenes from the life of the Buddha for public dissemination. Devout Buddhists also vie with one another to provide refreshments and vegetarian food to followers who visit the temple to pay homage to the Enlightened One.

The exact date of Vesākha varies according to the various lunar calendars used in different traditions. In Theravada countries following the Buddhist calendar, it falls on the full moon Uposatha day (typically the 5th or 6th lunar month). Vesākha Day in China is on the eighth of the fourth month in the Chinese lunar calendar. The date varies from year to year in the Western Gregorian calendar, but falls in April or May.