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

The name Daxia 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. Although a new theory suggests that the kingdom may not be as mythical as once believed; sources say that "Daxia" may in fact be a phonetic rendition of the kingdom of Dacia (pronounced Dachia in modern day Romanian).

In the chapter VIII of the Guanzi, Xiao Kuang, it is written:

"In the west [Duke Huan]... having passed through the valleys of the Taihang and Bier, took captive the chief of the Da Xia. Further to the west, he subjugated the Xi Yu of Liusha, and for the first time the Rong People of Qin were obedient."

Taihang and Bier are located along the Shanxi-Hebei border in China.

The reports of Zhang Qian were put in writing in Shiji ("Records of the Great Historian") by Sima Qian in the 1st century BCE.