Li Zhi succeeded his father, Emperor Taizong, in 649 and ruled Tang China under the temple name Gaozong until 683. His early government relied on senior ministers inherited from the previous reign, including his uncle Zhangsun Wuji. The dynasty consolidated its administrative institutions while continuing military expansion. A commentary of 653 established the Tang legal code as a model for later Chinese dynasties and neighbouring states.

A struggle over the imperial household transformed court politics. In 655 Gaozong removed Empress Wang and elevated Wu Zhao, later known as Wu Zetian, despite opposition from established ministers. Officials who resisted the change lost influence, and Zhangsun Wuji was eventually removed and forced to die. The new empress developed her own political following. Her prominence should not obscure Gaozong's role in choosing her and supporting the displacement of his father's advisers.

Tang armies achieved major victories during his reign. Su Dingfang defeated the Western Turkic ruler Ashina Helu in 657, expanding Chinese influence in Central Asia. In alliance with the Korean kingdom of Silla, Tang forces destroyed Baekje in 660 and Goguryeo in 668. These victories did not produce lasting control over the whole Korean peninsula: conflict with Silla followed, and Tang armies withdrew from its southern territories. Warfare with Tibet and renewed frontier resistance also qualified the apparent reach of the empire.

From around 660 Gaozong suffered recurring illness, and Wu increasingly handled state business. Their precise division of authority is debated; describing him simply as an inactive puppet understates the political choices made throughout his reign. Court ritual presented the couple as joint centres of authority, while succession disputes unsettled their household. Gaozong died in 683 and was buried at Qianling. His son succeeded him, but Wu retained power as empress dowager before establishing her own Zhou dynasty in 690.