Dev Diwali is a popular festival celebrated in the holy city of Varanasi, India. It falls on the full moon day in the Hindu month of Kartik, which usually falls in November or December. The festival is also known as 'Diwali of the Gods' or 'Festival of Lights' and is celebrated with great enthusiasm and fervor by the people of Varanasi.

On this day, the ghats (steps leading down to the river) of the river Ganges in Varanasi are lit up with thousands of earthen lamps, creating a beautiful and mesmerizing sight. The ghats are cleaned and decorated, and people offer prayers and light diyas (lamps) to the river Ganges to pay their respects to the river, which is considered sacred in Hinduism.

The festival is believed to have originated from a Hindu legend that says that on this day, the gods descend to the earth to bathe in the holy river Ganges. Dev Diwali is also said to mark the victory of Lord Shiva over the demon Tripurasura.

The festival is celebrated with great enthusiasm and zeal, and people decorate their houses with lamps and flowers. They also burst crackers and enjoy feasting with their family and friends. The festival is also an occasion for cultural programs, music, and dance performances.

Dev Diwali is a unique and beautiful festival that celebrates the spiritual and cultural richness of Varanasi, and attracts visitors from all over the world who come to witness the breathtaking beauty of the illuminated ghats and to participate in the festivities.