In 1799, after the French Revolution had quieted into the Thermidorean Reaction, a brilliant general named Napoleon Bonaparte overthrew the Directory and came into power as leader of the Consulate, beginning in 1799. Under Napoleon, France became a nationalist power, expanding its territory into Italy and exerting its influence over other powers. Napoleon consolidated his rule by suppressing rebellions in France, normalizing relations with the Church in the Concordat of 1801, and streamlining the French law system in the Napoleonic Code. By 1804, Napoleon was so powerful that he declared himself Emperor.

Defeating the various military coalitions the other powers of Europe threw against him, Napoleon won battle after battle: Marengo (1800), Austerlitz (1805), Jena-Auerstadt, and Friedland (1807). He built a vast empire of dependant states, forced Czar Alexander I to ally with him in the 1807 Treaty of Tilsit, and controlled the majority of Europe. Everywhere he went he spread the reforms and influence of the French Revolution to a remarkable extent. Just about the only blemish on his record during the first decade of the 19th century was a stunning naval loss to Britain at the Battle of Trafalgar Seeking to undermine Britain's sea power, Napoleon issued the Berlin Decree in 1806, imposing the Continental System on Europe, which was meant to stop European countries from trading with Britain. Instead of hurting Britain, the Continental System hurt Napoleon. Upset by Napoleonic rule, Germanic nationalism got its start, and the Germans began to move towards Romanticism as an intellectual rebellion against French Enlightenment ideas. In Spain, the attempt to impose the Continental System led to the Peninsular War, a protracted guerrilla war that diverted French forces from the rest of Europe. In 1810, Napoleon replaced his wife, Josephine, who had borne him no heir, with a younger wife, Marie Louise of Austria. They produced an heir, referred to as The King of Rome. Napoleon's happiness did not last, however, because at the end of 1810, Alexander I withdrew Russia from the Continental System. In 1812, Napoleon moved his Grand Army into Russia. Though Napoleons army pushed the Russians into constant retreat, the terrible Russian winter decimated Napoleon's Grand Army.