Colonial Assam (1826–1947) refers to the period of History of Assam between the signing of the Treaty of Yandabo and Independence of India when Assam was under the British colonial rule. The political institutions and social relations that were established or severed during this period continue to have a direct effect on contemporary events. The legislature and political alignments that evolved by the end of the British rule continued in the post Independence period. The immigration of farmers from East Bengal and tea plantation workers from Central India continue to affect contemporary politics, most notably that which led to the Assam Movement and its aftermath.
The region that came to be known as undivided Goalpara district came under British rule after the transfer of the Deewani from the Mughal Emperor on August 12, 1765. Due to tribal influences on the region the police thanas of Dhubri, Nageswari, Goalpara and Karaibari were placed under a special administrative unit called "North-Eastern Parts of Rangpur" (note: this Rangpur is now in present-day Bangladesh) in January 1822. The First Anglo-Burmese War commenced in 1824, and by March 28 the British had occupied Guwahati, when the Raja of Darrang (a tributary of the Ahom kingdom) and some petty chieftains submitted themselves to the British, who made rudimentary administrative arrangements by October 1824. The Burmese occupiers retreated from the Ahom capital of Rangpur in January 1825 and the nearly the whole of Brahmaputra Valley fell into British hands. In the war against the Burmese the Ahoms did not help the British. In 1828, the Kachari kingdom was annexed under the Doctrine of Lapse after the king Govinda Chandra was killed. In 1832, the Khasi king surrendered and the British increased their influence over the Jaintia ruler. In 1833, upper Assam became a British protectorate under the erstwhile ruler of the Ahom kingdom, Purandhar Singha, but in 1838 the region was formally annexed into the British empire. With the annexation of the Maran/Matak territory in the east in 1839, the annexation of Assam was complete.