The Battle of Trafalgar (October 21, 1805) is a naval engagement fought by the British Royal Navy against the combined fleets of the French Navy and Spanish Navy, during the War of the Third Coalition (August–December 1805) of the Napoleonic Wars (1803–1815).The battle is the most decisive British naval victory of the war.

Twenty-seven British ships of the line led by Admiral Lord Nelson aboard HMS Victory defeat thirty-three French and Spanish ships of the line under French Admiral Pierre-Charles Villeneuve off the southwest coast of Spain, just west of Cape Trafalgar.

The Franco-Spanish fleet loses twenty-two ships, without a single British vessel being lost.The British victory spectacularly confirms the naval supremacy that Britain had established during the previous century and is achieved in part through Nelson's departure from the prevailing naval tactical orthodoxy, which involves engaging an enemy fleet in a single line of battle parallel to the enemy to facilitate signaling in battle and disengagement, and to maximize fields of fire and target areas.

Nelson instead divides his smaller force into two columns directed perpendicularly against the larger enemy fleet, with decisive results.Nelson is mortally wounded during the battle, becoming one of Britain's greatest war heroes.

The commander of the joint French and Spanish forces, Admiral Villeneuve, is captured along with his ship Bucentaure.

Spanish Admiral Federico Gravina escapes with the remnant of the fleet and succumbs months later to wounds sustained during the battle.