The Battle of Leipzig (October 16-19, 1813), also called the Battle of the Nations, was the largest conflict in the Napoleonic Wars and one of the worst defeats suffered by Napoleon Bonaparte.

Following the disastrous campaign in Russia and defeats in the Peninsular War, the anti-French forces had cautiously regrouped as the Sixth Coalition, comprising Britain, Russia, Spain, Portugal, Prussia, Austria, Sweden and certain smaller German states.

Napoleon sought to re-establish his hold in Germany, winning two small victories at Lützen, on May 2 and Bautzen, on May 20-21 over Russo-Prussian forces. The victories led to a brief armistice but this lasted even less time than usual. The Allies rejoined the conflict under the command of Gebhard von Blucher, Crown Prince Charles of Sweden (Bernadotte) and Karl Schwarzenberg. The Allies tactics were to avoid clashes with Napoleon but seek meetings with his marshals, this led to victories at Grossbeeren, Kulm, Katzbach and at Dennewitz.

Napoleon failed to capture Berlin before withdrawing westwards, crossing the Elbe in late September and organizing his forces around Leipzig to protect his supply lines and meet the Allies. Napoleon arranged his army around Leipzig, but concentrating his force from Taucha through Stötteritz (where Napoleon placed his command) and then curving south-west to Lindenau. The Prussians advanced from Wartenburg, the Austrians and Russians from Dresden and the Swedish force from the north. In total, the French had around 190,000 soldiers and the Allies almost 330,000 with both sides having significant artillery.

The battle began on the 16th with an attack by 78,000 Allied troops from the south and 54,000 from the north, they achieved little and were soon forced back. The following day both forces merely skirmished as reinforcements arrived and were organized. On the 18th the Allies launched a huge assault from all sides, in over nine hours of fighting the French were slowly forced back towards Leipzig, both sides suffered heavy casualties and only the bravery of the French troops prevented a breakthrough. Napoleon saw that the battle could only end in defeat and on the night of the 18th-19th began to withdraw the majority of his army across the river Elster. The retreat went well until early afternoon when the single bridge was mistakenly destroyed, leaving the French rearguard to be caught by the Allies or to drown trying to swim the river.

Total casualties are uncertain, estimates range from 80,000 to 110,000 killed or wounded from both sides. Taking an estimate of 95,000 total, the Allies lost 55,000 and the French 40,000, with around 30,000 French taken prisoner. The battle ended the French Empire east of the Rhine and brought a number of German states over to the Allies.