The significant naval battle that took place in 1805 against Napoleon was the Battle of Trafalgar. This pivotal confrontation occurred on October 21, when British Admiral Horatio Nelson faced off against the combined fleets of France and Spain. Nelson's fleet achieved a decisive victory, effectively destroying Napoleon's hopes of invading Britain. The battle established British naval supremacy for the next century and reinforced the strategic importance of naval power in European conflicts. Nelson's leadership and tactics at Trafalgar are celebrated as exemplary in military history.