Tianxia (), literally meaning "(all) under Heaven", is a Chinese term for a historical Chinese cultural concept that denoted either the entire geographical world or the metaphysical realm of mortals, and later became associated with political sovereignty. In ancient China and imperial China, tianxia denoted the lands, space, and area divinely appointed to the Chinese sovereign by universal and well-defined principles of order. The center of this land was directly apportioned to the Chinese court, forming the center of a world view that centered on the Chinese court and went concentrically outward to major and minor officials and then the common subjects, tributary states, and finally ending with fringe "barbarians".
The center of this world view was not exclusionary in nature, and outer groups, such as ethnic minorities and foreign people, who accepted the mandate of the Chinese Emperor were themselves received and included into the Chinese tianxia. In classical Chinese political thought, the "Son of Heaven", having received the Mandate of Heaven, would nominally be the ruler of the entire world. Although in practice there would be areas of the known world which were not under the control of the Chinese monarch, in Chinese political theory the rulers of those areas derived their power from the Chinese monarch.
The larger concept of tianxia is closely associated with civilization and order in classical Chinese philosophy, and has formed the basis for the world view of the Chinese people and nations influenced by them since at least the first millennium BC. Tianxia has been applied by other realms in the Chinese cultural sphere, including Japan, Korea, and Vietnam.
As reconstructed by philosopher Zhao Tingyang, tianxia presupposed "inclusion of all" and implied acceptance of the world's diversities, emphasizing harmonious reciprocal dependence and ruled by virtue as a means for lasting peace. Academic Yan Xuetong writes that in the tianxia system, rulers relied on humane authority (in contrast to tyranny and military force) to win the hearts and minds of the people.