Winter swimming (dōng yǒng) is the practice of swimming outdoors in cold, often icy water during winter months—typically in lakes, rivers, or outdoor pools when temperatures are well below freezing. The term combines 冬 (dōng), meaning 'winter', and 泳 (yǒng), meaning 'to swim'; together, they literally mean 'winter swimming'. It’s a popular physical activity in northern China, especially in cities like Harbin and Beijing, where enthusiasts gather regularly despite sub-zero conditions.

This activity is widely regarded as a test of endurance and mental fortitude, and many participants believe it boosts immunity and circulation. While not a competitive sport per se, organized winter swimming associations hold annual events, including the famous Harbin International Winter Swimming Festival. Safety precautions—such as acclimatization, time limits, and supervision—are strongly emphasized due to the risks of hypothermia and cold shock.