The Battle of the Basque Roads, also known as the Battle of Aix Roads (French: Bataille de l'île d'Aix, also Affaire des brûlots, rarely Bataille de la rade des Basques), was a major naval battle of the Napoleonic Wars, fought in the narrow Basque Roads at the mouth of the Charente River on the Biscay coast of France. The battle, which lasted from 11–24 April 1809, was unusual in that it pitted a hastily-assembled squadron of small and unorthodox British Royal Navy warships against the main strength of the French Atlantic Fleet, the circumstances dictated by the cramped, shallow coastal waters in which the battle was fought. The battle is also notorious for its controversial political aftermath in both Britain and France.

In February 1809 the French Atlantic Fleet, blockaded in Brest on the Breton coast by the British Channel Fleet, attempted to break out into the Atlantic and reinforce the garrison of Martinique. Sighted and chased by British blockade squadrons, the French were unable to escape the Bay of Biscay and eventually anchored in the Basque Roads, near the naval base of Rochefort. There they were kept under observation during March by the British fleet under the dour Admiral Lord Gambier. The Admiralty, desiring an attack on the French fleet, ordered Lord Cochrane, an outspoken and popular junior captain, to lead an attack, over the objections of a number of senior officers. Cochrane organised an inshore squadron of fireships and bomb vessels, including a converted frigate, and personally led this force into Basque Roads on the evening of 11 April.

The attack caused little direct damage, but in the narrow waters of the channel the fireships panicked the sailors of the French fleet and most of their ships grounded and were left immobile. Cochrane expected Gambier to follow his attack with the main fleet, which could then destroy the vulnerable French force, but Gambier refused. Cochrane continued the battle over the next several days, successfully destroying several French ships, but with little support from Gambier. This allowed most of the French fleet to refloat and retreat up the Charente to safety. Gambier recalled Cochrane on 14 April and sent him back to Britain, withdrawing most of the inshore squadron at the same time, although scattered fighting continued until 24 April. The increasingly marginalised French fleet was badly damaged and trapped in its home ports; several captains were court-martialed for cowardice and one was shot.

In Britain the battle was celebrated as a victory, but many in the Navy were dissatisfied with Gambier's behaviour and Cochrane used his position as a Member of Parliament to publicly protest Gambier's leadership. Incensed, Gambier requested a court-martial to disprove Cochrane's accusations and the admiral's political allies ensured that the jury was composed of his supporters. After bitter and argumentative proceedings Gambier was exonerated of any culpability for failings during the battle. Cochrane's naval career was ruined, although the irrepressible officer remained a prominent figure in Britain for decades to come. Historians have almost unanimously condemned Gambier for his failure to support Cochrane; even Napoleon opined that he was an "imbécile".