The siege of Yorktown, also known as the Battle of Yorktown, the surrender at Yorktown, or the German battle (from the presence of Germans in all three armies), beginning on September 28, 1781, and ending on October 19, 1781, at Yorktown, Virginia, was a decisive victory by a combined force of the American Continental Army troops led by General George Washington and Gilbert du Motier, Marquis de Lafayette, and French Army troops led by Comte de Rochambeau over a British army commanded by British peer and Lieutenant General Charles Cornwallis. The culmination of the Yorktown Campaign, the siege proved to be the last major land battle of the American Revolutionary War in the North American region, as the surrender by Cornwallis, and the capture of both him and his army, prompted the British government to negotiate an end to the conflict.In 1780, about 5,500 French soldiers landed in Rhode Island to help their American allies fight the British troops who controlled New York City. Following the arrival of dispatches from France that included the possibility of support from the French West Indies fleet of the Comte de Grasse, disagreements arose between Washington and Rochambeau on whether to ask de Grasse for assistance in besieging New York or in military operations against a British army in Virginia. On the advice of Rochambeau, de Grasse informed them of his intent to sail to the Chesapeake Bay, where Cornwallis had taken command of the army. Cornwallis, at first given confusing orders by his superior officer, Henry Clinton, was eventually ordered to build a defensible deep-water port, which he began to do in Yorktown. Cornwallis' movements in Virginia were shadowed by a Continental Army force led by the Marquis de Lafayette.

The French and American armies united north of New York City during the summer of 1781. When word of de Grasse's decision arrived, both armies began moving south toward Virginia, engaging in tactics of deception to lead the British to believe a siege of New York was planned. De Grasse sailed from the West Indies and arrived at the Chesapeake Bay at the end of August, bringing additional troops and creating a naval blockade of Yorktown. He was transporting 500,000 silver pesos collected from the citizens of Havana, Cuba, to fund supplies for the siege and payroll for the Continental Army. While in Santo Domingo, de Grasse met with Francisco Saavedra de Sangronis, an agent of Carlos III of Spain. De Grasse had planned to leave several of his warships in Santo Domingo. Saavedra promised the assistance of the Spanish navy to protect the French merchant fleet, enabling de Grasse to sail north with all of his warships. In the beginning of September, he defeated a British fleet led by Sir Thomas Graves that came to relieve Cornwallis at the Battle of the Chesapeake. As a result of this victory, de Grasse blocked any reinforcement or escape by sea for Cornwallis and also disembarked the heavy siege guns required by the allied land forces. By late September, Washington and Rochambeau arrived, and the army and naval forces completely surrounded Cornwallis.

After initial preparations, the Americans and French built their first parallel and began the bombardment. With the British defense weakened, on October 14, 1781, Washington sent two columns to attack the last major remaining British outer defenses. A French column under Wilhelm of the Palatinate-Zweibrücken took Redoubt No. 9 and an American column under Alexander Hamilton took Redoubt No. 10. With these defenses taken, the allies were able to finish their second parallel. With the Franco-American artillery closer and its bombardment more intense than ever, the British position began to deteriorate rapidly. Cornwallis asked for capitulation terms on October 17. After two days of negotiation, the surrender ceremony occurred on October 19; Cornwallis was absent from the ceremony. With the capture of more than 7,000 British soldiers, negotiations between the United States and Great Britain began, resulting in the Treaty of Paris of 1783.

The battlegrounds are preserved and interpreted today as part of Colonial National Historical Park.