Haimen is a district located in Nantong, Jiangsu province, China. Situated on the northern bank of the Yangtze River estuary, it faces Shanghai across the water. The district covers an area of approximately 1,149 square kilometers and had a permanent population of nearly 1 million residents as of 2025.
Known by titles such as the "Gateway to the Yangtze River and the Yellow Sea" and "Little-Pudong," Haimen possesses a coastline along both the Yangtze River and the Yellow Sea. While historically recognized for its salt production and fishing industries, the district has transitioned into a significant port-based industrial hub in modern times.