The first Mongol invasion of Burma (Burmese: မွန်ဂို–မြန်မာ စစ် (၁၂၇၇–၁၂၈၇); Chinese: 元緬戰爭) were a series of military conflicts between Kublai Khan's Yuan dynasty, a division of the Mongol Empire, and the Pagan Empire that took place between 1277 and 1287. The invasions toppled the 250-year-old Pagan Empire, and the Mongol army seized Pagan territories in present-day Dehong, Yunnan and northern Burma to Tagaung. The invasions ushered in 250 years of political fragmentation in Burma and the rise of ethnic Tai-Shan states throughout mainland Southeast Asia.

The Mongols first demanded tribute from Pagan in 1271–1272, as part of their drive to encircle the Song dynasty of China. When King Narathihapate refused, Emperor Kublai Khan himself sent another mission in 1273, again demanding tribute. It too was rejected. In 1275, the emperor ordered the Yunnan government to secure the borderlands in order to block an escape path for the Song, and permitted a limited border war if Pagan contested. Pagan did contest but its army was driven back at the frontier by the Mongol army in 1277–1278. After a brief lull, Kublai Khan in 1281 again turned his attention to Southeast Asia, demanding tribute from Pagan, the Khmer Empire, Đại Việt and Champa. When the Burmese king again refused, the emperor ordered an invasion of northern Burma. Two dry season campaigns (1283–1285) later, the Mongols had occupied down to Tagaung and Hanlin, forcing the Burmese king to flee to Lower Burma. The Mongols organized northern Burma as the province of Zhengmian.

Truce negotiations began in 1285, and ended with Narathihapate finally agreeing to submit in June 1286. The Burmese embassy, received by the emperor in Beijing in January 1287, agreed to a treaty that acknowledged the suzerainty of the Mongol Empire over the Pagan Empire and annual payments in taxes to the Yunnan government in exchange for the evacuation of Mongol troops from northern Burma, but the treaty never really took effect as Narathihapate was assassinated in July 1287, and no authority who could honor the treaty emerged. The Mongol command at Yunnan now deemed the imperial order to withdraw void, and ordered an invasion of central Burma. They may not have reached Pagan, and even if they did, after having suffered heavy casualties, they returned to Tagaung.

The Pagan Empire disintegrated and anarchy ensued. The Mongols, who probably preferred the situation, did nothing to restore order in the next ten years. In March 1297, they accepted the voluntary submission of King Kyawswa of Pagan although he controlled little beyond the capital city of Pagan (Bagan). But Kyawswa was overthrown nine months later, and the Mongols were forced to intervene, leading to their second invasion in 1300–1301.

Marco Polo reported the first invasions (1277–1287) in his travelogue, Il Milione. The Burmese referred to the invaders as the Taruk (after the central Asian Turkic troops that largely made up the Mongol invasion army); today, the term Taruk (တရုတ်) refers to the Han Chinese instead. King Narathihapate is unkindly remembered in Burmese history as Taruk-Pye Min, ("the King who Fled from the Taruk").

In the 13th century, the Pagan Empire, along with the Khmer Empire, was one of the two main empires in mainland Southeast Asia. For much of its history, Pagan's neighbor to the northeast was not China but the independent Dali Kingdom and its predecessor Nanzhao, both with Dali as their capital city. Dali-based kingdoms were a power in their own right, at times allying themselves with the Tibetan Empire to their west and at other times with China's Tang and Song dynasties. Indeed, Nanzhao's mounted armies ventured deep into what is today Burma and may have been behind the founding of the medieval city of Pagan and the Pagan dynasty itself.

Between the newly conquered Mongol territory and Pagan were a wide swath of borderlands stretching from present-day Dehong, Baoshan and Lincang prefectures in Yunnan as well as the Wa and Palaung regions (presumably in present-day northern Shan State), which Pagan and Dali had both claimed and exercised overlapping spheres of influence. Then as now, the borderlands mostly consist of forbidding terrains of high mountain ranges.

The Mongol Empire first arrived at the doorstep of the Pagan Empire in 1252 by invading the Dali Kingdom in its attempt to outflank Song China. The Mongol armies captured the capital, Dali, on 7 January 1253, and went on to pacify much of the kingdom by 1257.