Gai Jatra (Newar: गाईजात्रा), also known by its endonym Sa Paru (Nepal Bhasa: सा पारु), is a Nepalese festival celebrated mainly in the Kathmandu valley by the Newar people. The festival is celebrated in honour of their immediate relatives who have died during the previous year. Various groups of children dressed up as cows and in other religious drags are organized throughout various cities.

It is generally celebrated in the month of Bhadra (August/September). The date is set according to the lunar Nepal Samabat calendar and falls on the first day of the dark fortnight of the month of Gunla.

Gai Jatra was started by King Pratap Malla during his reign from 1641 to 1671 AD. His teenage son Chakravartendra Malla died an untimely death and the queen grieved the loss of her son. King Pratap Malla started this tradition to help ascend his son to the next life and cheer the grieving queen and families of those whose loved ones had died.

The festival is Sa Paru in Nepal Bhasa. In Nepal Bhasa, Sa translates to cow and Paru translate to Pratipada tithi (the first day of the fortnight, according to Hindu calendar system). The festival is called this because it is celebrated on Bhadra māsa śukla pakṣa pratipada tithi and the children dress as cows. It is popularly known as Gai Jatra (lit. cow carnival) in the Nepali language and across other parts of Nepal and the world.

In the Hindu religion, Gai (Cow) is sacred like a Lakshmi and viewed as a mother. The children of those whose families had died would come out to Hanuman Dhoka Palace and the Newar priest performs the prayers for those passed. The children usually wear long skirts and must have a tulle belt around their waist with the ends hanging on both their right and left sides that drag on the ground while walking. It is necessary that it drag because it touches the ground (Earth) for the loved ones who died to ascend from Earth to heaven. This is a festival of dragging clothes while walking. The children also wear headdresses that have a cow drawn on them which is important, and they wear a moustache drawn on their faces. The Jatra is supposed to be religious for the Newar community to help loved ones pass from Earth to heaven and cheer those left behind. The parade of drag is done in the morning by children and in the evening with caricature and stand-up comedy by Hanuman Dhoka Dabali for the grieving Queen and others.

Since the 1600s, the caricatures and jokes have evolved and also include political satires to make it more interesting on TV shows, usually the male standup comedians wear female clothes and perform both male and female parts of the play, this is a fun event for the Newar community as well as for all other Nepalese communities.

Gai Jatra is mainly celebrated in the cities of Kathmandu valley—Kathmandu, Patan, and Bhaktapur. The celebrataion of the festival has also spread to other parts of the country which have a significant Newar community.

Kathmandu is considered the main source of this festival because the king who started this festival was from this city. After the show presented to the queen was a success, it became an annual program to present the queen with this festival. As time passed and the king and queen died, the festival was passed on from generation to generation. In Kathmandu, people celebrate it with much happiness and many more programs than those in Patan. The procession goes around the city to different parts of the suburbs and the inner urban areas to present their devotion to their loved ones. The people involved in this profession get small packets with fruits, sweets, oats, and other food items to help them on their tour around the city by many people watching the festival and by their loved ones.