The Napoleonic Wars (1803–1815) were a series of conflicts fought between the First French Empire under Napoleon (1804–1815), and a fluctuating array of European coalitions. The wars originated in political forces arising from the French Revolution (1789–1799) and from the French Revolutionary Wars (1792–1802) (the War of the First Coalition (1792–1797) and the War of the Second Coalition (1798–1802)), and produced a period of French domination of Continental Europe. There were seven Napoleonic Wars, five named after the coalitions that fought Napoleon, plus two named for their respective theatres: (i) the War of the Third Coalition (1803–1806), (ii) the War of the Fourth Coalition (1806–1807), (iii) the War of the Fifth Coalition (1809), (iv) the War of the Sixth Coalition (1813–1814), (v) the War of the Seventh Coalition (1815), (vi) the Peninsular War (1807–1814), and (vii) the French invasion of Russia (1812).

Upon realising the Coup of 18 Brumaire, whereby he became the First Consul of France in 1799, Napoleon assumed control of the politically chaotic French First Republic. He then organised a financially stable French state with a strong bureaucracy and a professional army. War broke about soon after, with Britain declaring war on France on 18 May 1803, ending the Peace of Amiens, and forming a coalition made up of itself, Sweden, Russia, Naples, and Sicily. Frank McLynn argues that Britain went to war in 1803 out of a "mixture of economic motives and national neuroses – an irrational anxiety about Napoleon's motives and intentions." The British fleet under Admiral Nelson decisively crushed the joint Franco-Spanish navy in the Battle of Trafalgar in October 1805. This victory secured British control of the seas and prevented a planned invasion of Britain. In December 1805, Napoleon defeated the allied Russo-Austrian army at Austerlitz, effectively ending the Third Coalition and forcing Austria to make peace. 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 soon defeated the Prussians at Jena and the Russians at Friedland, bringing an uneasy peace to the continent. The treaty failed to end the tension, and war broke out again 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.

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. However, Napoleon escaped in February 1815, and reassumed control of France for around one hundred days. The allies formed the Seventh Coalition, 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.