The Kamata Kingdom Assamese: কমতা ৰাজ্য, romanized: ˈkʌmətɑ; in the eastern Sivalik Hills, emerged in western Kamarupa probably when Sandhya, a ruler of Kamarupanagara, moved his capital west to Kamatapur sometime after 1257 CE. Since it originated in the old seat of the Kamarupa kingdom, and covered most of the western parts of it, the kingdom is also sometimes called as Kamarupa-Kamata.

It covered a region corresponding to present-day undivided districts of Kamrup, Goalpara, Jalpaiguri, and Cooch Behar district in India and Rangpur and northern parts of Mymensingh in Bangladesh. The rise of the Kamata kingdom marked the end of the ancient period in the history of Assam and the beginning of the medieval period. The last rulers were the Khens, who were later displaced in 1498 by Alauddin Hussain Shah, the ruler of the Bengal Sultanate. Though Hussain Shah developed extensive administrative structures, he lost political control to a confederation of Baro-Bhuyan within a few years.

In 1515, Biswa Singha removed the Baro-Bhuyan confederacy and established the Koch dynasty. The Koches were the last to call themselves Kamateshwar (the rulers of Kamata), but due to the far-reaching extensive influence and expansions the kingdom is sometimes called the Koch Kingdom. In the following century the kingdom split in Koch Bihar and Koch Hajo. The eastern kingdom, Koch Hajo, was absorbed into the Ahom kingdom in the 17th century. The western portion of the Kamata kingdom, Koch Bihar continued to be ruled by a branch of the Koch dynasty and later merged with the Indian territory after the independence of India from the British domain. The boundary between Koch Bihar and Koch Hajo is approximately the boundary between West Bengal and Assam today.

Sandhya, was a ruler of Kamarupanagara, the capital of the erstwhile Kamarupa. After withstanding an attack from Malik Ikhtiyaruddin Iuzbak in which Iuzbak was killed (1257) Sandhya moved his capital to Kamatapur, near present-day Cooch Behar town. Sandhya styled himself Kamateswara and the kingdom came to be known as Kamata.

Pratapdhvaj was a minister of Singhadhvaj when he usurped power. At his death, his cousin Dharmanarayan seized power. He was challenged by Pratapdhvaj's son Durlabhnarayan and they decided to settle. Durlabhnarayan assumed power Kamrup, Goalpara, Jalpaiguri, Koch Bihar, along with the capital Kamatapur, while Dharmanarayan retained Rangpur and Mymensingh. As part of the settlement in about 1330, Durlabhnarayan received from Dharmanarayan the custody of fourteen families of Brahmans and Kayasthas, one among whom was Candivara, the great-great-grandfather of Sankardev. The court poets of Durlabhnarayan (Hema Saraswati and Harivara Vipra) and Indranarayan produced literary works that are considered to be the first examples of Early Assamese.

The invasion of Assam by Sikandar Shah (1357–1390) weakened Indranarayan. Though Sikander Shah had to retreat from central Assam because of an attack on Bengal by Firuz Shah Tughlaq, Indranarayana was sufficiently damaged that a Bhuyan from Darrang, Arimatta, was able to usurp power.

The Khen dynasty, of Kheng-Bhutanese origin, replaced the weak rulers of Kamata kingdom following Arimatta in the middle of the 15th century. Niladhvaj Khen, the first king, united several Baro-Bhuyan chieftains of the area and removed the last of Arimatta's successors—Mriganka. There were only three Khen rulers:

The last king, Nilambar expanded the kingdom to include the present Koch Bihar districts of West Bengal and the undivided Kamrup and Darrang districts of Assam and northern Mymensingh in Bangladesh as well as eastern parts of Dinajpur district, though he was removed by Alauddin Husain Shah in 1498.^{[citation needed]}