Admiral Charles Napier vanquishes the navy of the Portuguese usurper Dom Miguel at the third Battle of Cape St. Vincent.

The Battle of Cape St. Vincent was a naval encounter off Cape St. Vincent between a Liberal fleet under the command of British naval officer Charles Napier against a Miguelite fleet under the command of Portuguese naval officer Manuel Marreiros, which was fought on 5 July 1833 during the Liberal Wars and resulted in a decisive victory for the Liberal fleet. Over the course of the battle, the Liberal fleet, despite being significantly outnumbered by the Miguelite fleet and lacking any ships of the line compared to the Miguelite four, managed to close with the Miguelites, board their ships and engage in hand-to-hand combat. The early exchange of cannon fire between the two fleets went on for some time before Napier decided that his numerically inferior squadron could not last long against the Miguelite fleet, and sailed his ships directly towards the Miguelite fleet.This decision by Napier was the deciding factor in the outcome of the battle, and the Miguelite crews proved no match for the Liberal crews, most of them being former Royal Navy personnel that had been discharged and sought service under Pedro I of Brazil. The battle resulted in four Miguelite ships of the line, one frigate and one corvette being captured, and the remainder of the Miguelite fleet retreating from the engagement. The action took place in context of the Liberal Wars, a Portuguese civil war fought between the King of Portugal, Dom Pedro, and a pretender named Don Miguel, whose supporters were called Miguelites. The battle had a decisive effect on the war, since the Miguelite fleet at Cape St. Vincent was the last significant naval force that Don Miguel could muster, his other naval forces being lost in the Battle of the Tagus on 11 July 1831 against a French fleet led by Albin Roussin. The Miguelite-held Lisbon, deprived of any chance to be resupplied via the sea, quickly capitulated.

Admiral is one of the highest ranks in some navies. In the Commonwealth nations and the United States, a "full" admiral is equivalent to a "full" general in the army or the Air Force, and is above vice admiral and below admiral of the fleet, or fleet admiral. In NATO, admirals have a rank code of OF-9 as a four-star rank.