The St. Elizabeth's flood of 1421 was a flooding of the Grote Hollandse Waard, an area in what is now the Netherlands. It takes its name from the feast day of Saint Elisabeth of Hungary which was formerly 19 November.
It ranks 20th on the list of worst floods in history.
During the night of 18/19 November 1421 a heavy storm near the North Sea coast caused the dikes to break in a number of places and the lower-lying polder land was flooded. A number of villages were swallowed by the flood and were lost, causing between 2,000 and 10,000 casualties. The dike breaks and floods caused widespread devastation in Zeeland and Holland.