Nagas (Sanskrit:नाग) were a group who spread throughout India during the period of the epic Mahabharata. Anthropologist Gelek Lonbsang believes they have distant ancestry with East Asians based on their similar physical features. The demi-god tribe called Suparnas (in which Garuda belonged) were arch-rivals of the Nagas. However, the Nagas near Kashmir seems to be the original abode of all of them. Places like Anantnag attests this theory.
Nagas had kingdoms in Nagaland and Andhra Pradesh. Arjuna's wife Ulupi was from one of such Naga kingdom (in Gangetic Plain) Arjuna's another wife Chitrangada who also was known to Ulupi was from Manipur. There are now many Naga worshiping places in South India, especially in Andhra Pradesh and Kerala.
Naga race was almost exterminated by Janamejaya, the Kuru king in Arjuna's line, who conducted the massacre of Nagas at Takshasila. This massacre was stopped by Astika, a Brahmin whose mother was a Naga (Vasuki's sister Jaratkaru).
According to a story in Matsya Puran, quoted in chapter X of a book India of the Dark Ages the Nagas ruled for 100 years as renegades (this because they were Buddhist). Later, it is said they purified themselves with water of the Ganga, performed ten Asvamedha Yagyas and were thus accepted, into the folds of Vaishnavism.
एतानि नवनामानि च महात्मनाम् । Etāni navanāmāni cha mahātmanām
According to historian Ram Swarup Joon, The facts are, however, different. This dynasty belonged to Madrak Jat gotra of Yadav Vansh and was devotees of Shiva. They had a number of ruling dynasties such as Takshak Nag, Bachak Nag, Kilkil Nag, Karkotaka, Kaliramna etc all of which are Jat gotras. Mathura, Padmavati and Kantipur were capitals of Naga dynasty. Nagas of Padmavati were called Taank, which is also a Jat gotra, and are found in 24 villages near Sonipat.
In chapter 29 of "India of the Dark Ages" the ancestor of Tanks is mentioned as Raja Gajvkatra. In chapter 42 of the same book it is mentioned that Malla Jat Republic extended from Eastern Punjab to the Ganga and Yodhya republic extended into Rajasthan. Nagpur belonged to the Nagas. Nagar Brahmins also originated from there.
Naga gotra (clan) of Jats are found in Nagaur and Sikar districts of Rajasthan and Khargone district of Madhya Pradesh. The villages inhabited by Naga Jats in Sikar district are - Dujod, Kanwarpura, Rampura, Sikar. In Madhya Pradesh Naga Jats are found in Badwah and Khargone.