St. Peter's flood (Dutch: Sint-Pietersvloed, German: Petriflut) refers to two separate storm tides that struck the coasts of Netherlands and Northern Germany in 1651. During the first storm tide, on 22 February, the East Frisian island of Juist was split in two. During the second disaster, on 4–5 March, the city of Amsterdam was flooded.

In the past, the two storm tides were thought to have been a single event. The two disasters were confused with each other because two different calendars were in use at the time. The Julian calendar was still in use in Northern Germany and some parts of the Netherlands, while the Gregorian calendar had already been adopted in Holland, Zeeland and other parts of the Netherlands.

The year 1651 was something of an annus horribilis for flooding, with many disastrous floods in Europe. In the Netherlands, for instance, another storm tide that struck during the night of 25–26 February broke through a number of dikes and flooded large parts of the eastern Netherlands.