The Treaty of Stettin or Alliance of Stettin was the legal framework for the occupation of the Duchy of Pomerania by the Swedish Empire during the Thirty Years' War. Concluded on 25 August (O.S.) or 4 September 1630 (N.S.), it was predated to 10 July (O.S.) or 20 July 1630 (N.S.), the date of the Swedish Landing. Sweden assumed military control, and used the Pomeranian bridgehead for campaigns into Central and Southern Germany. After the death of the last Pomeranian duke in 1637, forces of the Holy Roman Empire invaded Pomerania to enforce Brandenburg's claims on succession, but they were defeated by Sweden in the ensuing battles. Some of the Pomeranian nobility had changed sides and supported Brandenburg. By the end of the war, the treaty was superseded by the Peace of Westphalia (1648) and the subsequent Treaty of Stettin (1653), when Pomerania was partitioned into a western, Swedish part, and an eastern, Brandenburgian part.

The Swedish Empire was the period in Swedish history spanning much of the 17th and early 18th centuries during which Sweden became a European great power that exercised territorial control over much of the Baltic region. The beginning of the period is usually taken as the reign of Gustavus Adolphus, who ascended the throne in 1611, and its end as the loss of territories in 1721 following the Great Northern War.