Early History of Tripura is as old as Indian mythology. There are different theories about the origin of the name of Tripura. According to mythology, legends and the Rajmala is that the name derived from the mighty king Tripur. He ruled over the kingdom some where about 1600-1700 BC, before the commencement of great Mahabharata war. But this theory is not accepted by all section of the people.
In the early period, the Emperor Ashoka some where in the area of modern Uttarakhand, Tripura was added in his kingdom. Emperor was supposed to have visited and defeated the kingdom and spread his boundary upto this highland of Himalaya. There was one kingdom by the name of Kirata Rajya, in the Himalayan mountain ranges of Uttarakhand, the kingdom of Tripura was also used to be known as Kirata desha, or Kirata Rajya as per the Rajmala.
According to Hindu mythology there was a mighty powerful demon king by the name Tripurasur. He was so powerful that all the kings of India were subdued by him. According to the Shiva Purana, it is stated that- one day Narada, the celestial man wanted to know from his father Lord Brahma how such mighty Tripur king was defeated. Then Brahma narrated the story this way, -Tripur was ardent devotee of Lord Shiva. He would not take even a sip without worshipping Shiva.
Tripurasur had constructed huge temple of Shiva in his country. Every house of under his control had Shiva deity; all the citizens were loyal followers of Shiva. No other gods were worshipped and had any temple, nor there ever any festival for any other gods. There was no irreligious activity in the kingdom of Tripur, all sacred scripture like Veda; Purana etc. were studied all the time. When other gods tried their luck in the kingdom of Tripur, all of them did not get any regard and any worship from the people of Tripur kingdom. This annoyed all the other gods except then Shiva and felt humiliated at the hands of people of Tripur kingdom.
At this all the gods came to Brahma and sought his intervention. He said that he can not go against the Veda and righteousness as king Tripur was following all these. At this point Brahma told the story-any one who is fervent devotee of Shiva he can not be killed.
Now again all the gods sought the help and suggestion from Lord Vishnu. They are asked to do Yagna for Shiva, a Makhpati was born. They requested him to destroy and kill Tripur. But he replied that he could do nothing to a person who is the diehard follower of Shiva. Then Vishnu made Shivalinga and worshipped and meditated for Shiva nonstop day and night. Shiva was pleased by this and blessed hem with Trishul, gada, and many demons and power rakshas soldiers were born out of it; all of them were ordered to go for a fight with Tripur and kill him, taking all the arms and ammunition that was given by Lord Shiva. But as soon as they entered the kingdom of king Tripur all them were burnt to ashes by the power of Lord Shiva.
When Vishnu got the news of this, he was saddened and made a deep meditation to get the answer of it. He asked all the gods to make a Shiva linga and worship him for three nights. After that Vishnu himself sat for meditation and worship of Shiva, when a man was born out of his body by the name of Mundi, he was then ordered to go to the kingdom of Tripur and preach irreligion. For this Vishnu wore a false religious book containing 16,000 hymns. It was against the Veda and Purana, against the virtues, manners, ethics, and code of conduct. Mundi first preached from this false scripture among the people of kingdom of Tripur, then Narada in disguise became the disciple, and the same was intimated to Tripurasur. He was very much pleased, glad and happy to learn the false irreligious scripture of Vishnu. Tripur was then made ardent disciple of Mundi, and was hypnotized to do all irreligious and acts of vices and immoral. The people of Tripur thus became anti-Veda and anti-traditional religion; there was anarchy, chaos, immoral, un chastity.
It was possible that this kingdom was probably also known as Kirata-Pura or city of Kirata by the Indo-Aryan speakers, which later transformed to Kirati-pura to Kar-tipura to Kar-tripura to Tripura. The ruler of the state was probably named as Tripur, by the name of the kingdom; it was tradition in earlier days to name the king or kingdom in reciprocal way. It was the mighty king of Tripura, who ruled over most of the plain lands and defeated neighbouring kings, who then was termed as Asura, and later became famous. This was how the name of Tripura state had come into existence in ancient time.
The earliest location of Tripura was at the present day's tripartite confluence, at Allahabad, who came here after being pushed south wards by Aryan invaders from Harappa. But during the reign of lunar dynasty king Yayati, his one of his son Druhya was exiled to north east wards, to the present place of Uttarakhand.
There are ample of linguistic and ethnical evidence that once Tripura kingdom was situated at the Himalayan mountain ranges. Tripuri people migrated out from the Mourung area to present Assam, then from there to Kachhar and finally to the present location of Tripura, by around 590 AD.