The Siege of Pirna (or Investment of Pirna) took place in 1756 as part of the Prussian invasion of Saxony during the Seven Years' War. Following the occupation of the capital Dresden by Frederick the Great on 9 September the Saxon army had withdrawn south and taken up position at the fortress of Pirna under Frederick von Rutowski. The Saxons hoped to receive relief from the Austrian army which was across the border in neighbouring Bohemia under Marshal Browne.