Huai'an, formerly Huaiyin, is a prefecture-level city in central Jiangsu Province in Eastern China. As of 2020, the built-up area (metro) of its 3 central urban districts had 2,544,767 inhabitants and the prefecture-level city as a whole had 4,556,230 inhabitants, down from 4.8 million in 2010.

The Huai River, formerly romanized as the Hwai, is a major river in China. It is located about midway between the Yellow River and Yangtze, the two longest rivers and largest drainage basins in China, and like them runs from west to east. Historically draining directly into the Yellow Sea, floods have changed the course of the river such that it now primarily discharges into the Yangtze. The Huai is notoriously vulnerable to flooding.