L'Hermite's expedition was a French naval operation launched in 1805 during the Napoleonic Wars. The operation was intended as both a commerce raiding operation against the British trading posts of West Africa and as a diversion to the Trafalgar campaign. Sailing from Lorient in October 1805 with one ship of the line, two frigates and a corvette, Commodore Jean-Marthe-Adrien L'Hermite was under orders to intercept and destroy British traders and slave ships off the West African coast and await reinforcements under Jérôme Bonaparte which were to be used in the invasion and capture of one of the British trading forts for use as a permanent French naval base from which further raiding operations could be conducted. It was also hoped by the French naval command that L'Hermite might draw some of the large British fleet maintained off Cadiz away from the blockade to allow the French and Spanish allied fleet trapped in the harbour to escape.
Although L'Hermite achieved minor successes against individual British shipping, his force was too small to have a serious impact on British trade in the region and the promised reinforcements failed to materialise in the aftermath of the destruction of the Cadiz fleet at the Battle of Trafalgar on 21 October 1805, ten days before L'Hermite sailed although before news of the battle had reached Lorient. In early January 1806, L'Hermite managed to capture a small British naval brig but was still unable to make any significant impact on British trade operations. In the spring of 1806 L'Hermite withdrew across the Atlantic, taking on supplies and effecting repairs in neutral Brazil. During the return journey to France in August 1806, the squadron was caught in a major hurricane and one frigate was severely damaged, limping to a port in the United States for repairs. The rest of the squadron continued on to France, L'Hermite reaching Brest in his flagship Régulus. The other frigate was intercepted by a British blockade squadron on 27 September 1806 and captured in the Bay of Biscay.