Tong'an is a district on the northern mainland portion of Xiamen, a city in Fujian Province, China. It covers an area of 657.59 square kilometres (253.90 square miles).
The district faces Quemoy County of the Republic of China across the water. It is bordered by Anxi and Nan'an to the north, Jimei to the south, and lies east of Lianxiang and Changqin to the west.