The First Toungoo Empire (Burmese: တောင်ငူခေတ်, [tàʊɴŋù kʰɪʔ], lit. "Toungoo Period"; also known as the Second Burmese Empire in traditional historiography, or simply the Taungoo dynasty) was the dominant power in mainland Southeast Asia in the second half of the 16th century. At its peak, Toungoo "exercised suzerainty fromManipur to the Cambodian marches and from the borders of Arakan to Yunnan" and was "the largest empire in the history of Southeast Asia." The "most adventurous and militarily successful" dynasty in Burmese history was also the "shortest-lived."
The empire grew out of the principality of Toungoo, a minor vassal state of Ava until 1510. The landlocked petty state began its rise in the 1530s under Tabinshwehti who went on to found the largest polity in Myanmar since the Pagan kingdom by 1550. His more celebrated successor Bayinnaung then greatly expanded the empire, conquering much of mainland Southeast Asia by 1565. He spent the next decade keeping the empire intact, putting down rebellions in Siam, Lan Xang and the northernmost Shan states. From 1576 onwards, he declared a large sphere of influence in westerly lands—trans-Manipur states, Arakan and Ceylon. The empire, held together by patron-client relationships, declined soon after his death in 1581. His successor Nanda Bayin never gained the full support of the vassal rulers, and presided over the empire's precipitous collapse in the next 18 years.