Napoleonic Wars: The Battle of Waterloo results in the defeat of Napoleon Bonaparte by the Duke of Wellington and Gebhard Leberecht von Blücher forcing him to abdicate the throne of France for the second and last time.

The Battle of Waterloo was fought on Sunday, 18 June 1815, near Waterloo in the United Kingdom of the Netherlands, now in Belgium. A French army under the command of Napoleon was defeated by two of the armies of the Seventh Coalition. One was a British-led coalition consisting of units from the United Kingdom, the Netherlands, Hanover, Brunswick, and Nassau, under the command of the Duke of Wellington (referred to by many authors as the Anglo-allied army or Wellington's army). The other was a larger Prussian army under the command of Field Marshal von Blcher (also referred to as Blcher's army). The battle marked the end of the Napoleonic Wars. The battle was contemporaneously known as the Battle of Mont Saint-Jean (France) or La Belle Alliance ("the Beautiful Alliance" Prussia).Upon Napoleon's return to power in March 1815, many states that had opposed him formed the Seventh Coalition and began to mobilise armies. Wellington and Blcher's armies were cantoned close to the northeastern border of France. Napoleon planned to attack them separately in the hope of destroying them before they could join in a coordinated invasion of France with other members of the coalition. On 16 June, Napoleon successfully attacked the bulk of the Prussian army at the Battle of Ligny with his main force, causing the Prussians to withdraw northwards on 17 June, but parallel to Wellington and in good order.

Napoleon sent a third of his forces to pursue the Prussians, which resulted in the separate Battle of Wavre with the Prussian rear-guard on 1819 June, and prevented that French force from participating at Waterloo. Also on 16 June, a small portion of the French army contested the Battle of Quatre Bras with the Anglo-allied army. The Anglo-allied army held their ground on 16 June, but the withdrawal of the Prussians caused Wellington to withdraw north to Waterloo on 17 June.

Upon learning that the Prussian army was able to support him, Wellington decided to offer battle on the Mont-Saint-Jean escarpment across the Brussels road, near the village of Waterloo. Here he withstood repeated attacks by the French throughout the afternoon of 18 June, aided by the progressively arriving Prussians who attacked the French flank and inflicted heavy casualties. In the evening, Napoleon assaulted the Anglo-allied line with his last reserves, the senior infantry battalions of the Imperial Guard. With the Prussians breaking through on the French right flank, the Anglo-allied army repulsed the Imperial Guard, and the French army was routed.

Waterloo was the decisive engagement of the Waterloo campaign and Napoleon's last. According to Wellington, the battle was "the nearest-run thing you ever saw in your life". Napoleon abdicated four days later, and coalition forces entered Paris on 7 July. The defeat at Waterloo ended Napoleon's rule as Emperor of the French and marked the end of his Hundred Days return from exile. This ended the First French Empire and set a chronological milestone between serial European wars and decades of relative peace, often referred to as the Pax Britannica. The battlefield is located in the Belgian municipalities of Braine-l'Alleud and Lasne, about 15 kilometres (9.3 mi) south of Brussels, and about 2 kilometres (1.2 mi) from the town of Waterloo. The site of the battlefield today is dominated by the monument of the Lion's Mound, a large artificial hill constructed from earth taken from the battlefield itself; the topography of the battlefield near the mound has not been preserved.

The Napoleonic Wars (1803–1815) were a series of major global conflicts pitting the French Empire and its allies, led by Napoleon I, against a fluctuating array of European states formed into various coalitions. It produced a period of French domination over most of continental Europe. The wars stemmed from the unresolved disputes associated with the French Revolution and its resultant conflict. The wars are often categorised into five conflicts, each termed after the coalition that fought Napoleon: the Third Coalition (1805), the Fourth (1806–07), the Fifth (1809), the Sixth (1813–14), and the Seventh (1815).

Napoleon, upon ascending to First Consul of France in 1799, had inherited a republic in chaos; he subsequently created a state with stable finances, a strong bureaucracy, and a well-trained army. In December 1805 Napoleon achieved what is considered his greatest victory, defeating the allied Russo-Austrian army at Austerlitz. At sea, the British severely defeated the joint Franco-Spanish navy in the Battle of Trafalgar on 21 October 1805. This victory secured British control of the seas and prevented the invasion of Britain. Concerned about increasing French power, Prussia led the creation of the Fourth Coalition with Russia, Saxony, and Sweden, which resumed war in October 1806. Napoleon quickly defeated the Prussians at Jena and the Russians at Friedland, bringing an uneasy peace to the continent. The peace failed, though, as war broke out in 1809, with the badly prepared Fifth Coalition, led by Austria. At first, the Austrians won a stunning victory at Aspern-Essling, but were quickly defeated at Wagram, which was the bloodiest battle in history until the battle of Leipzig.

Hoping to isolate and weaken Britain economically through his Continental System, Napoleon launched an invasion of Portugal, the only remaining British ally in continental Europe. After occupying Lisbon in November 1807, and with the bulk of French troops present in Spain, Napoleon seized the opportunity to turn against his former ally, depose the reigning Spanish royal family and declare his brother King of Spain in 1808 as José I. The Spanish and Portuguese revolted with British support and expelled the French from Iberia in 1814 after six years of fighting.

Concurrently, Russia, unwilling to bear the economic consequences of reduced trade, routinely violated the Continental System, prompting Napoleon to launch a massive invasion of Russia in 1812. The resulting campaign ended in disaster for France and the near destruction of Napoleon's Grande Armée.

Encouraged by the defeat, Austria, Prussia, Sweden, and Russia formed the Sixth Coalition and began a new campaign against France, decisively defeating Napoleon at Leipzig in October 1813 after several inconclusive engagements. The Allies then invaded France from the east, while the Peninsular War spilled over into southwestern France. Coalition troops captured Paris at the end of March 1814 and forced Napoleon to abdicate in April. He was exiled to the island of Elba, and the Bourbons were restored to power. But Napoleon escaped in February 1815, and reassumed control of France for around one hundred days. After forming the Seventh Coalition, the allies defeated him at Waterloo in June 1815 and exiled him to the island of Saint Helena, where he died six years later.The Congress of Vienna redrew the borders of Europe and brought a period of relative peace. The wars had profound consequences on global history, including the spread of nationalism and liberalism, the rise of Britain as the world's foremost naval and economic power, the appearance of independence movements in Latin America and subsequent decline of the Spanish and Portuguese Empires, the fundamental reorganization of German and Italian territories into larger states, and the introduction of radically new methods of conducting warfare, as well as civil law. After the end of the Napoleonic Wars there was a period of relative peace in continental Europe, lasting until the Crimean War in 1853.