The Yakthung or Limbu tribes and clans belong to the Kirati nation or to the Kirat confederation. They are indigenous to the hill and mountainous regions of east Nepal between the Arun and Mechi rivers to as far as Southern Tibet, Bhutan and Sikkim.
The name Limbu is an exonym of an uncertain origin. The word Limbu roughly translates as an archer or 'the bearer of bows and arrows'. They call themselves Yakthumba/Yakthung (in Limbu language). They are also known as Shong, Xong or Drenjongka. Their estimated population of 700,000 is centered in the districts of Sankhuwasabha, Tehrathum, Dhankuta, Taplejung, Morang, Sunsari, Jhapa, Panchthar and Ilam in Nepal. These districts are all within the Mechi and Kosi zones also known as Limbuwan. Portions of the Limbu population are also located in the East and West districts of Sikkim. A smaller number are scattered throughout the cities of Darjeeling and Kalimpong in West Bengal, India, and in North and South Sikkim and Bhutan.
Limbu Clans and Tribes are divided into the Lhasa gotra (from Lhasa, Tibet) and Yunan gotra (from Yunan, China). The Limbu are known as Yakthung Thi-bon or Des Limbu (ten Limbu), from which thirteen Limbu sub-groups have emerged. According to legend, five of the groups came from Yunan, China and the other eight from Lhasa, Tibet.
Unlike the caste system which was brought to the Nepal region after the Hindu invasion, a caste system is not practised among the Limbu people and Limbu sub-groups. However, there are numerous different clans and family-sects.
The Chinese text called Po-ou-Yeo-Jing translated in 308 AD refers to the Yi-ti-Sai (barbarians bordering on the north), a name which is an exact equivalent of Kiratas.

Limbu language
Main articles: Limbu language and Limbu script
Limbu (Limbu:Yakthungpan; "Language of the Yakthung") is a Sino-Tibetan/Tibeto-Burman language spoken in Nepal, Sikkim, Kashmir and parts of Northern India by the Limbu and Monpa community.
Limbu language went through its own unique evolution from the Tibetan and Devanagiri writing systems. Far more Limbus are literate in Nepali than in Limbu, thus many Limbu publications are accompanied by Nepali translation.
Limbu language is one of the major spoken and written languages of Nepal, Sikkim, and other parts of Northern India. Today, linguists have reached the conclusion that pronominalization is an indigenous development of the Tibeto-Burman language, and Limbu language bears a close resemblance with Khambu Sampang and other unique Tibetan dialects. Limbu language has four main dialects: Panchthare, Tamarkhole, Phedape and Chatthare.
Before the introduction of Sirijonga script among Limbu Kiratas, Rong script was popular in East Nepal, especially in the early Maurong state. Sirijonga script nearly disappeared for 800 years, but it was brought back into practice by Te-Ongsi Sirijonga Thebe of Tellok Sinam.

Limbu culture
Limbu women with traditional clothing and traditional tongba drink.
Limbus practice many of their own rituals. They believe that lineage is not transmitted patrilineally. Rather, a woman inherits her mother's goods, and when she marries and lives with her husband she brings with her the deities that will then be recognized as the household deities.
Limbu bury their dead and observe for two to three days through practiced death rituals. The length of the mourning period varies depending on the gender of the deceased. Weddings, mourning, gift exchanges, and settlement of conflicts involve consumption of liquor, especially the Limbu traditional beer popularly known as Tongba. Dancing parties are arranged for visitors to the village. These affairs give the young Limbu girls and boys a chance to meet and enjoy dancing and drinking.

Wedding practices
Limbus generally marry within their own community (Jones and Jones, 1976). Cross-cousin marriage is not allowed in Limbu culture. Marriage between a man and the widow of his elder brother can take place if they mutually agree. Marriage between a man and a woman outside the clan is also possible either by arrangement or by mutual consent of the man and woman in question. It is conventionally said that the customs and traditions of Limbus were established in the distant past by Sawa Yethang (council of eight kings). The marriages are mostly arranged by parents or they can also result when a man elopes with a woman. Asking for a woman's hand is an important ceremony. In that system, the woman can ask for anything, including an amount of gold, silver, etc. This confirms to the woman's family that the man is financially secure enough to keep their daughter happy. A few days after the wedding, the man's family members have to visit the woman's house with a piglet and some alcoholic and non-alcoholic beverages, depending upon the financial standard of his house. The most important ceremonies of a Limbu wedding take place in the groom's house rather than the bride's because the bride has to stay with her husband. There are two special dances in this ceremony, one is called "yalakma" or dhan nach in Nepali (rice harvest dance) and "Kelangma" or Chyabrung in Nepali. The Yalakma is characterized by men and women dancing in a slow circle, whereas the Kelangam consists of complex footwork synchronized with the beat of the drums. Anyone can join the dance, which can last for many hours. The Yalakma can also be a celebration of the harvest season or other social occasions.

Limbu religion & festivals
The Limbus follow the Kirant Mundhum oral 'scripture' similar to the Bön, shaman. However, their religion is also influenced by Tibetan Buddhism and Hinduism. They have their own distinct religion known as "Yuma Samyo" or "Yumaism". They also have many different classes of ritual specialists, of which "Phedangma", "Yema/Yeba", and "Shamba" are some. Their supreme deity is Tagera Ningwaphuma, but the deity Yuma (literally: "Grandmother" or "Mother Earth") is the most important and popular among the Limbus and is worshiped in all occasions. Yuma is the mother of all the Limbus, therefore one regards his or her mother as a goddess. Their religion is enshrined in the evergreen Cynodondactylon (Dubo) grass. Traditionally, the Limbu bury their dead, but due to the influence from their Hindu neighbours, cremation is becoming more popular. Limbu people also have their own clergy, such as Phedangma, Samba, Yeba (male) Yewa-Yema (female). According to the Nepal Census of 2001, out of 359,379 Limbu, 86.29% were identified as practising the traditional Kiranti religion, and 11.32% were identified as Hindu and other religions. Modern Limbus have also been influenced by Christianity, especially those living in parts of India.