Thanh Giong is one of the Tu Bat Tu, the Four Immortals of Vietnamese folk religion, and his legend recounts a child born to an elderly couple who does not speak or walk until the age of three, when word arrives that the kingdom faces invasion from the north; the boy suddenly rises, asks for an iron horse, an iron whip and an iron suit of armour, and grows to giant size within a single day, then rides out and single-handedly routs the invading army before ascending directly to heaven from a mountain, choosing eternal divine status over any earthly reward for his service. The legend is set during the semi-legendary reign of the Hung kings, Vietnam's traditional founding dynasty, and functions as a foundational patriotic narrative, giving Vietnamese national identity a divinely sanctioned defender figure whose sudden emergence in a moment of existential crisis remains one of the most recognisable and frequently retold stories in Vietnamese culture.