The siege of Pilsen or Battle of Pilsen was a siege of the fortified city of Pilsen in Bohemia carried out by the forces of the Bohemian Protestants led by Ernst von Mansfeld. It was the first major battle of the Thirty Years' War. The Protestant victory and subsequent capture of the city enlarged the Bohemian Revolt.

Plzeň, also known in English and German as Pilsen, is a city in the Czech Republic. About 78 kilometres west of Prague in western Bohemia, it is the fourth most populous city in the Czech Republic with about 181,000 inhabitants, and about 323,184 people in its urban area.