Chhath is a festival dedicated to the Sun God. This festival is a way of thanking the Sun for bestowing the bounties of life on earth and fulfilling particular wishes. Worship of the Sun has been practised in southern Nepal, as well as elsewhere in the world, from time immemorial. Worship of the Sun has been described in the Rig Veda, the oldest Hindu scripture, and hymns praying to the Sun are found in the Vedas.

In the ancient epic Mahabharata, references to worshipping of the Sun by Draupadi, wife of the Pandavas, are found. It was believed that worshipping of the Sun would help cure several diseases, including leprosy, and also ensure longevity and prosperity of the family members, friends, and elders. It is also believed that Chhath was started by the great Danveer (generous giver of donations) Karna, sired by the Sun God.

Also called Dala Chhath, it is an ancient and major festival in the Tarai. It is celebrated twice a year: once in the summers (May-July), called the Chaiti Chhath, and once in the winters (September-November) within a week after Deepawali, called the Kartik Chhath. The latter is more popular because winters are the usual festive season in Nepal, and Chhath being an arduous observance, requiring the worshippers to fast without water for more than 24 hours, is easier to observe during winters. Chhath is a ritual bathing festival that follows a period of abstinence and ritual segregation of the worshipper from the main household for four days.