Chhath is an ancient Indo-Nepalese Hindu festival, native to eastern India and southern Nepal. It is celebrated, especially in the Indian states of Bihar, Jharkhand,West Bengal and Purvanchal; and Koshi, Gandaki, Bagmati, Lumbini, and Madhesh provinces of Nepal. In major urban centres like Delhi, Mumbai, Kolkata, Janakpur, and Kathmandu, the Indian and Nepali diaspora actively participates in celebrating Chhath, preserving their cultural heritage. The festival is also celebrated by the diaspora in countries such as the United States, Australia, Singapore, the United Arab Emirates, Canada, Mauritius, Japan, and the United Kingdom.

During Chhath Puja, prayers are dedicated to the solar deity, Surya, to express gratitude for the blessings of life on Earth and to seek the fulfilment of personal wishes. The Hindu goddess Chhathi Maiya (or Chhathi Mata)—the sixth form of Prakriti and Surya's sister—is also worshipped during the festival. It is celebrated for six days after Deepavali or Tihar, until the sixth day of the lunar month of Kartika (October or November) in the Hindu calendar (Vikram Samvat), which is why it is called 'Surya Shashti Vrata'. The rituals are observed over three nights and four days, and include holy bathing, fasting, abstaining from drinking water as a vrata (devotion), standing in water, and offering prasada (prayer offerings of food) and arghya to the rising and setting of the Sun. Some devotees also perform a prostration march as they head towards the riverbanks. All devotees prepare similar prasada and offerings.

Chhath Puja is also marked by the preparation and offering of a variety of traditional and sattvic (pure and vegetarian) dishes that are cooked without onion or garlic. These food items hold cultural and religious importance, often passed down through generations.

Four of the most important traditional prasadas (offerings) offered during Chhath Puja are:

These recipes are not only offerings but also symbolize purity, devotion, and cultural richness associated with the Chhath festival.

Environmentalists have claimed that the festival of Chhath is one of the most eco-friendly religious festivals.

Chhath Puja is dedicated to Surya, the Sun God, as it is thought that the sun is visible to every being and is the basis of life of all creatures on Earth. Chhathi Maiya (or Chhathi Mata) is also worshipped on this day. According to Vedic astrology, Chhathi Maiya grants children long life and good health by shielding them from illnesses and diseases.

Chhath Puja is a folk festival that lasts four days. It starts with Kartik Shukla Chaturthi and ends with Kartik Shukla Saptami. Chhath is celebrated twice a year: