Minh Tông was born in 1300 as Trần Mạnh, the only surviving son of emperor Trần Anh Tông and imperial consort Huy Tư, who was the daughter of general Trần Bình Trọng. According to "Đại Việt sử ký toàn thư", the precise birthday of Prince Trần Mạnh was 21 August in the lunar calendar, only one day after the death of Trần Hưng Đạo who was the most important minister in the early Trần dynasty and the main commander of second and third wars of resistance by Đại Việt against Mongol Empire, which made him one of the most famous heroes of Vietnam. The other sons of Anh Tông all died at a young age so the Emperor had his relative and important figure of the Trần clan, Trần Nhật Duật, raise Trần Mạnh in the hope that he would survive and began a key figure in the family. Indeed, Prince Trần Mạnh was well looked after due to the wholehearted devotion of Trần Nhật Duật.