Ancient Kamrup was period of Kamrup spanning from prehistoric to early medieval times, consisting of Western Assam and North Bengal which under Kamarupa kingdom covered entire Brahmaputra valley, North Bangladesh, Bhutan and Purnea.
The ancient epics Ramayana and Mahabharata refer to this region as Pragjyotish, not as Kamrup. The Puranas, written after the Mahabharata, mention the same Pragjyotish region as Kamrup. The Vishnu Purana describes Kamrup to spread 450 miles in all directions from the Kamakhya Temple (today in Gauhati). The Kalika Purana calls Kamakhya Temple the center or heart of Kamrup. The Yogini Tantra composed thereafter gives the geographical area of Kamrup as the entire Brahmaputra Valley, Bhutan, Rangpur (Bangladesh), Mymensing (Bangladesh), Cooch Behar. The Chinese pilgrim to India, Xuanzang, gives a detailed account of ancient Kamrup. Staying for a period of three months in what is current Guwahati, he observes life, culture and politics in Kamrup. The first millennium of the common era sees the expansion of the geographical, political and cultural influence of Kamrup. Ancient Kamrup has four geographical divisions collectively known as Kamarupa Pithas.
Modern Kamrup region served as capital of ancient Kamrup. Chinese traveller Xuanzang visited the capital area and observed that land was low and moist and that the crops were regular. Cocoa-nuts and jack-fruits grew abundantly and were appreciated by the people. The climate was genial.
The primary language used by Aryan people of land was old Kamrupi language, which also act as lingua franca among non-Aryan peoples. Kamrupi language was a variety of eastern Maithili and Xuanzang noted that the spoken language of Kamrup differed only a little from the language spoken in mid-India i.e. Magadha and Mithila. During historic times it was through Mithila that Aryan culture and civilization spread into the Kamrup. From Kamrup in the north that the Aryans gradually spread towards the south to Gauda, north of the Ganges, and to Samatata, south of the Ganges.