According to Irish legend, Saint Patrick drove snakes out of Ireland.
The story says that Patrick stood on a hill and banished the snakes after they attacked him during a period of fasting. It became one of the best-known legends associated with his life and is frequently represented in Saint Patrick's Day imagery.
Natural history provides an important qualification: post-glacial Ireland has no native snakes in the archaeological record. The legend is therefore not generally treated as a literal account of a historical mass expulsion.
Some historians and folklorists interpret the snakes symbolically, perhaps as representations of pagan beliefs or evil. The story may also have developed from older Christian traditions in which saints defeat serpents. It remains a legend rather than a detail recorded in Patrick's own writings.