The Pearl River Delta Metropolitan Region is the low-lying area surrounding the Pearl River estuary, where the Pearl River flows into the South China Sea. Referred to as the Guangdong–Hong Kong–Macao Greater Bay Area in official documents, the region is one of the most densely populated and urbanized regions in the world, and is considered a megacity by numerous scholars. It is currently the wealthiest region in Southern China and one of the wealthiest regions in China along with the Yangtze River Delta in Eastern China and Jingjinji in Northern China. Most of the region is part of the Pearl River Delta Economic Zone, which is a special economic zone of China.

Jing-Jin-Ji cluster is an expanded urban agglomeration consisting of Beijing (Jing), Tianjin (Jin), and Hebei (Ji). It is the biggest urban agglomeration region in North China, including an economic region surrounding the municipalities of Beijing and Tianjin, and along the coast of the Bohai Sea. This emerging region is rising as a northern metropolitan region rivaling the Pearl River Delta in the south and the Yangtze River Delta in the east. In 2020, Jingjinji had a total population of 110 million people, comparable to that of the Philippines.