The Deluge is a name commonly assigned in history of Poland to series of war in 17th century which left Poland in ruins. In more strict sense deluge refers only to Swedish invasion and occupation of country, in wider it applies to whole series of misfortunes started by uprising of Cossacks in 1648 and ending in either 1656, 1660 or even in 1667. Before The Deluge Poland was Central European power. During the wars however Poland lost estimated 1/3 of population (relatively higher losses than during World War II) and power status.

The misfortunes were started in 1648 by Bohdan Chmielnicki. Although the cossacks were defeated in 1651 in Battle of Beresteczko, their rebellion gave pretext to Russians to invade and occupy the eastern half of Polish-Lithuanian Commonwealth in 1655. The Swedes invaded and occupied the rest in the same year. The Swedes were driven back in 1657, and the Russians were finally defeated in 1662. The struggle over Ukraine ended with peace in Andrusovo 1667, with the help of Turkish intervention due to their claims in the Crimean. Forces from Prussia and Siebenburgen were also defeated, but Prussia gained a formal recognition of independence and ceased to be Polish vassal.

The Deluge also stopped era of Polish tolerance, since most of the invaders were non-Catholic, with expulsion of the Polish brethren as clear sign of it.

The Deluge is described in a novel of Henryk Sienkiewicz under the same title.

See also: Northern War, Treaty of Oliva