The Polish–Lithuanian–Teutonic War, also known as the Great War, was a war that occurred between 1409 and 1411 between the Teutonic Knights and the allied Kingdom of Poland and Grand Duchy of Lithuania. Inspired by the local Samogitian uprising, the war began with a Teutonic invasion of Poland in August 1409. As neither side was ready for a full-scale war, Wenceslaus IV of Bohemia brokered a nine-month truce.

After the truce expired in June 1410, the military-religious monks were decisively defeated in the Battle of Grunwald, one of the largest battles in medieval Europe. Most of the Teutonic leadership was killed or taken prisoner. Although they were defeated, the Teutonic Knights withstood the siege on their capital in Marienburg (Malbork) and suffered only minimal territorial losses in the Peace of Thorn (1411). Territorial disputes lasted until the Peace of Melno of 1422.

However, the Knights never recovered their former power, and the financial burden of war reparations caused internal conflicts and economic decline in their lands. The war shifted the balance of power in Central Europe and marked the rise of the Polish–Lithuanian union as the dominant power in the region.