Saint Patrick reportedly drove snakes out of Ireland.
This is a famous legend rather than a documented historical event. Medieval tradition says Patrick stood on a hill, used a bell or staff, and banished the snakes into the sea. The story helped portray him as a powerful Christian missionary who defeated older pagan forces.
There is also a zoological reason the tale is doubtful: Ireland has no native wild snakes. The island was covered by ice during the last Ice Age, and snakes did not recolonise it after the glaciers retreated. Small populations of captive or introduced snakes can exist, but they are not native Irish wildlife.
Many historians interpret the snakes symbolically, with “snakes” representing pagan beliefs or evil. Patrick’s own fifth-century writings do not mention driving snakes from Ireland, so the story belongs to later folklore rather than his surviving biography.