The Treaty of Sugauli is a historic international treaty signed between the British East India Company and the Kingdom of Nepal. Drafted on December 2, 1815, and formally ratified on March 4, 1816, the treaty ended the Anglo-Nepalese War of 1814–1816. The conflict arose from the expansionist campaigns of both the British and Nepal, which led to border disputes over the Terai region. The treaty solved the problem of war by establishing "perpetual peace and friendship" and redefining Nepal's political and territorial boundaries.
The treaty's key mechanism involved significant territorial concessions by Nepal, which lost approximately one-third of its land. Article V required Nepal to renounce all claims to the countries west of the Kali River, including Kumaon and Garhwal. Nepal also ceded territories east of the Mechi River, including Sikkim, and large parts of the Terai lowlands. Other provisions included the establishment of a British Resident in Kathmandu and the right for Britain to recruit Gurkhas for military service.
The treaty connects directly to the ongoing India-Nepal border dispute over the Kalapani-Lipulekh-Limpiyadhura region. This dispute hinges on the interpretation of Article V and the precise origin of the Kali River, which the treaty established as Nepal's western boundary. The treaty was partially changed by the Boundary Treaty of 1860, which restored some western Terai lands to Nepal as a reward for its assistance to the British during the Indian Rebellion of 1857. Despite these later adjustments, the Sugauli Treaty remains the foundational legal document governing the modern India-Nepal boundary.