Treaty ports (Chinese: 商埠; Japanese: 条約港) were the port cities in China and Japan that were opened to foreign trade mainly by the unequal treaties forced upon them by Western powers, as well as cities in Korea opened up similarly by the Qing dynasty of China (before the First Sino-Japanese War) and the Empire of Japan.

The British established their first treaty ports in China after the First Opium War by the Treaty of Nanking in 1842. As well as ceding the island of Hong Kong to Great Britain in perpetuity, the treaty also established five treaty ports at Shanghai, Guangzhou (Canton), Ningbo, Fuzhou, and Xiamen (Amoy). The following year the Chinese and British signed the Treaty of the Bogue, which added provisions for extraterritoriality and the most favored nation status for the latter country. Subsequent negotiations with the Americans (1844 Treaty of Wanghia) and the French (1844 Treaty of Whampoa) led to further concessions for these nations on the same terms as the British.

The second group of treaty ports was set up following the end of the Second Opium War (Arrow War) in 1860 and eventually, more than 80 treaty ports were established in China alone, involving many foreign powers.

Foreigners all lived in prestigious sections newly built for them on the edges of existing port cities. They enjoyed legal extraterritoriality, as stipulated in the unequal treaties. Some of these port areas were directly leased by foreign powers such as in the foreign concessions in China, effectively removing them from the control of local governments.

Western images of the Chinese treaty ports focus on the distinctive geography of the "bund", a long narrow strip of land in a prime location on the waterfront where the businesses, offices, warehouses, and residences of all foreigners were located. The Shanghai Bund was the largest and most famous. The North Riverbank in Ningbo (nowadays known as the Old Bund), was the first in China, opening in 1844, 20 years before the Shanghai bund. A typical bund contained British, German, French, American, Japanese, and other nationals.

The bund was a self-governing operation with its own shops, restaurants, recreational facilities, parks, churches, courts, police, and local government. The facilities were generally off-limits to the natives. The British, who by far dominated foreign trade with China, normally were the largest presence. Businessmen and officials typically brought their own families with them and stayed for years but sent their older children back to England for education.

Chinese sovereignty was only nominal. Officially, the foreign powers were not allowed to station military units in the bund, but in practice, there often was a warship or two in the harbor.

The treaty port system in China lasted approximately one hundred years. It began when the First Opium War ended in 1842. The major powers involved were the British, the French, and the Americans, although by the end of the 19th century all the major powers were involved.