Napoleonic Wars: War of the Third Coalition: Battle of Cape Finisterre: An inconclusive naval action is fought between a combined French and Spanish fleet under Admiral Pierre-Charles Villeneuve of France and a British fleet under Admiral Robert Calder.

The Napoleonic Wars (1803–1815) were a global series of conflicts fought by a fluctuating array of European coalitions against the French First Republic (1803–1804) under the First Consul followed by the First French Empire (1804–1815) under the Emperor of the French, Napoleon Bonaparte. The wars originated in political forces arising from the French Revolution (1789–1799) and from the French Revolutionary Wars (1792–1802) and produced a period of French domination over Continental Europe. The wars are categorised as seven conflicts, five named after the coalitions that fought Napoleon, plus two named for their respective theatres: the War of the Third Coalition, War of the Fourth Coalition, War of the Fifth Coalition, War of the Sixth Coalition, War of the Seventh Coalition, the Peninsular War, and the French invasion of Russia.

The War of the Third Coalition was a European conflict lasting from 1805 to 1806 and was the first conflict of the Napoleonic Wars. During the war, France and its client states under Napoleon I and its ally Spain opposed an alliance, the Third Coalition, which was made up of the United Kingdom, the Austrian Empire, the Russian Empire, Naples, Sicily, and Sweden. Prussia remained neutral during the war.

In the Battle of Cape Finisterre off Galicia, Spain, the British fleet under Admiral Robert Calder fought an indecisive naval battle against the combined Franco-Spanish fleet which was returning from the West Indies. In the ensuing battle the British captured two Spanish ships of the line, but failed to prevent the joining of French Admiral Pierre de Villeneuve's fleet to the squadron of Ferrol and to strike the shattering blow that would have freed Great Britain from the danger of an invasion. Calder was later court-martialled and severely reprimanded for his failure and for avoiding the renewal of the engagement on 23 and 24 July. At the same time, in the aftermath Villeneuve elected not to continue on to Brest, where his fleet could have joined with other French ships to clear the English Channel for an invasion of Great Britain.