Nantong is a prefecture-level city in southeastern Jiangsu province, China. Located on the northern bank of the Yangtze River, near the river mouth. Nantong is a vital river port bordering Yancheng to the north; Taizhou to the west; Suzhou, Wuxi and Shanghai to the south across the river; and the East China Sea to the east. Its population was 7,726,635 as of the 2020 census, 3,766,534 of whom lived in the built-up area made up of three urban districts.

Yancheng, formerly known as Yandu, is a prefecture-level city in northeastern Jiangsu province, People's Republic of China. As the city with the largest jurisdictional area in Jiangsu, Yancheng borders Lianyungang to the north, Huai'an to the west, Yangzhou and Taizhou to the southwest, Nantong to the south, and the Yellow Sea to the east. Formerly a county, the current Yancheng city was founded on January 18, 1983.