The Great Flood of Gun-Yu (traditional Chinese: 鯀禹治水), also known as the Gun-Yu myth, was a major flood event in ancient China that allegedly continued for at least two generations, which resulted in great population displacements among other disasters, such as storms and famine. People left their homes to live on the high hills and mounts, or nest on the trees. According to mythological and historical sources, it is traditionally dated to the third millennium BCE, during the reign of Emperor Yao. Archaeological evidence of an outburst flood on the Yellow River (possibly among the worst anywhere in the world in the past 10,000 years) has been dated to about 1920 BCE (several centuries later than the traditional recorded beginning of the Xia dynasty), and is suggested to have been the basis for the myth.
Treated either historically or mythologically, the story of the Great Flood and the heroic attempts of the various human characters to control it and to abate the disaster is a narrative fundamental to Chinese culture. Among other things, the Great Flood of China is key to understanding the history of the founding of both the Xia dynasty and the Zhou dynasty, it is also one of the main flood motifs in Chinese mythology, and it is a major source of allusion in Classical Chinese poetry.
The story of the Great Flood plays a dramatic role in Chinese mythology, and its various versions present a number of examples of the flood myth motif around the world. Flood narratives in Chinese mythology share certain common features, despite being somewhat lacking in internal consistency as well as incorporating various magical transformations and divine or semi-divine interventions like Nüwa. For example, the flood usually results from natural causes rather than "universal punishment for human sin". Another distinct motif of the myth of the Great Flood of China is an emphasis on the heroic and praiseworthy efforts to mitigate the disaster; flooding is alleviated by constructing dikes and dams (such as the efforts of Gun), digging canals (as devised by Yu the Great), widening or deepening existing channels, and teaching these skills to others.