Nanjing County is under the jurisdiction of Zhangzhou City, Fujian Province. Located in the northwest of Zhangzhou City, with an area of 1962 square kilometers and a population of 360000, it has 11 towns under its jurisdiction; According to the data of the seventh population census, as of 0:00 on November 1, 2020, the permanent resident population of Nanjing County was 305259. The urban area of the county seat is 8.12 square kilometers, and the built-up area is 8.1 square kilometers.

Nanjing County, known as Lanshui County in ancient times, was established in 1322 in the second year of the reign of Emperor Zhizhi of the Yuan Dynasty, and is under the jurisdiction of Zhangzhou City, Fujian Province. It was renamed as Nanjing County in 1356. It was under the jurisdiction of Zhangzhou City in 1985. In August 2019, Zhangzhou High-tech Industrial Development Zone realized the integration of the zone and the land. The 18 administrative villages of Jingcheng Town, on the south bank of the West Stream of the Jiulong River, were under the jurisdiction of Zhangzhou High-tech Industrial Development Zone.

Nanjing is one of the key overseas Chinese towns and important ancestral places of Taiwanese in Zhangzhou City. There are more than 30000 overseas Chinese and more than 1 million Taiwanese in Nanjing. The ancestral places of Taiwan celebrities such as Xiao Wanchang and Lu Xiulian are all in Nanjing. In 2019, the "top ten" counties (cities) in Fujian province's county economic development.

In 2020, the gross domestic product (GDP) of Nanjing County will be 32.88 billion yuan.