Tong sui, also known as tim tong, is a collective term for any sweet soup or custard served as a dessert typically at the end of a meal in Chinese cuisine. Tong sui originated in the Lingnan region of China, including Guangdong, Guangxi, Hainan, Hong Kong, Macau, and some parts of other provinces in China. Therefore, in the narrow sense, the term tong sui is used to refer to soupy desserts from Lingnan, while occasionally it is also used in the broad sense, referring to any soupy dessert in Chinese-speaking regions.

Soup is a primarily liquid food, generally served warm or hot, that is made by combining ingredients of meat or vegetables with stock, milk, or water. Hot soups are additionally characterized by boiling solid ingredients in liquids in a pot until the flavors are extracted, forming a broth. Soups are similar to stews, and in some cases there may not be a clear distinction between the two; however, soups generally have more liquid (broth) than stews.