Ta-Hia, or Daxia (Chinese:大夏) is the name given in antiquity by the Chinese to the territory of Bactria.

The name Ta-Hia appears in Chinese from the 3rd century BCE to designate a mythical kingdom to the West, possibly a consequence of the first contacts with the expansion of the Greco-Bactrian Kingdom, and then is used by the explorer Zhang Qian in 126 BCE to designate Bactria.

The reports of Zhang Qian were put in writing in the Shiji ("Records of the Great Historian") by Sima Qian in the 1st century BCE. They describe an important urban civilization of about one million people, living in walled cities under small city kings or magistrates. Ta-Hia was an afluent country with rich markets, trading in an incredible variety of objects, coming as far as Southern China. By the time Zhang Xian visited Ta-Hia, there were no longer a major king, and the Bactrian were suzerains to the nomadic Yuezhi, who were settled to the north of their territory beyond the Oxus. Overall Zhang Qian depicted a rather sophisticated but demoralized people who were afraid of war.

Following these reports, the Chinese emperor Wu-Ti was informed of the level of sophistication of the urban civilizations of Ferghana, Bactria and Parthia, and became interested in developing commercial relationship them: "The Son of Heaven on hearing all this reasoned thus: Ferghana (Ta-Yuan) and the possessions of Bactria (Ta-Hia) and Parthia (An-Xi) are large countries, full of rare things, with a population living in fixed abodes and given to occupations somewhat identical with those of the Chinese people, but with weak armies, and placing great value on the rich produce of China" (Han Shu, Former Han History).

These contacts immediately led to the dispatch of multiple embassies from the Chinese, initiating the development of the Silk Road.