The Algeciras campaign (also known as the Battle of Algeciras or Battles of Algeciras) was an attempt by a French Navy squadron from Toulon under Counter-Admiral Charles-Alexandre Léon Durand Linois to join a Franco-Spanish fleet at Cadiz in June-July 1801 during the War of the Second Coalition prior to a planned expedition to either Egypt or Portugal. To reach Cadiz, Linois's squadron had to pass the British naval base at Gibraltar, which contained the squadron tasked with blockading Cadiz. The British squadron was commanded by Rear-Admiral Sir James Saumarez. After a successful voyage between Toulon and Gibraltar in which a number of British vessels were captured, the squadron anchored at Algeciras, a fortified port city within sight of Gibraltar across Gibraltar Bay. On 6 July 1801, Saumarez attacked the anchored squadron, in the First Battle of Algeciras. Although severe damage was inflicted on all three French ships of the line, none could be successfully captured and the British were forced to withdraw without HMS Hannibal, which had grounded and was subsequently seized by the French.

In the aftermath of the first battle, both sides set about making urgent repairs and calling up reinforcements. On 9 July a fleet of five Spanish and one French ship of the line and several frigates arrived from Cadiz to safely escort Linois's squadron to Cadiz, and the British at Gibraltar redoubled their efforts to restore their squadron to fighting service. In the evening of 12 July the French and Spanish fleet sailed from Algeciras, and the British force followed them, catching the trailing ships in the Second Battle of Algeciras and opening fire at 11:20. A confused night action followed in which the British ship HMS Superb cut through the disorganised Franco-Spanish rearguard, followed by the rest of Saumarez's force. In the confusion one French ship was captured, a Spanish frigate sank and two huge 112-gun Spanish first rates collided and exploded, killing as many as 1,700 men. The following morning the French ship Formidable came under attack at the rear of the combined squadron, but successfully drove off pursuit and reached Cadiz safely.

Ultimately the French and Spanish fleets were successful in their aim of uniting at Cadiz, albeit after heavy losses, but they were still under blockade and in no position to realise either the Egyptian or the Portuguese plans. The two battles, "generally regarded as a single linked battle", proved decisive in cementing British control of the Mediterranean Sea and condemning the French Army in Egypt to defeat, totally unsupported by reinforcements from the French Navy.

On 1 August 1798, a British fleet surprised and almost completely destroyed the French Mediterranean Fleet at the Battle of the Nile in the aftermath of the successful French invasion of Egypt. This immediately reversed the strategic situation in the Mediterranean Sea, eliminating the French fleet based at Toulon as a significant threat and granting the British and their allies in the War of the Second Coalition naval dominance in the region. Over the next three years, British and allied squadrons enforced blockades against all significant French and Spanish naval bases in the region, including Alexandria, Corfu and Malta but particularly the significant harbours at Toulon and Cadiz. This drastically limited the movement of French troops and military materials across the Mediterranean, with the result that Malta and Corfu were captured and the army in Egypt was steadily reduced in size and effectiveness.

In January 1801, in an attempt to increase the size of the French Mediterranean Fleet and to reinforce the beleaguered Egyptian garrison, First Consul Napoleon Bonaparte ordered a squadron of seven ships of the line to sail from Brest on the Atlantic coast to the Mediterranean under Counter-Admiral Honoré Joseph Antoine Ganteaume. The squadron made three unsuccessful attempts to reach Egypt, eventually retiring to Toulon in late July 1801. During the final effort, Ganteaume's squadron sailed from Toulon on 27 April 1801 with instructions to briefly secure local naval supremacy around Elba to allow a seabourne invasion to go ahead, before travelling on into the Eastern Mediterranean. During these operations, Ganteaume discovered that several ships in his force were dangerously undermanned, and therefore decided to consolidate his crews and send three ships of the line, Formidable, Indomptable and Desaix, and the frigate Créole back to Toulon.

The presence of this force at Toulon enabled the French to plan a secondary operation using Ganteaume's new arrivals. A deal had been brokered earlier in the year between Bonaparte and Charles IV of Spain for the Spanish government to provide six ships of the line from the Cadiz fleet to the French Navy. Orders were given that the new squadron at Cadiz was to be joined by the three ships of the line detached from Ganteaume's squadron, as well as the frigate Muiron under the overall command of Counter-Admiral Charles-Alexandre Léon Durand Linois. This force of nine French ships, accompanied by six promised vessels from the Spanish fleet, was then to fulfill one of two mooted plans: the first was a large scale attack on Lisbon. Portugal and Spain were engaged in the War of the Oranges and Lisbon was a major British trading port: the French admiral Kerguelen had estimated some years earlier that an attack there could seize as much as "2 millions" of British goods and shipping. The other planned operation, adopted following the end of the War of the Oranges on 2 June, was for the force to resupply Egypt using soldiers stationed at Italian ports.

To facilitate the transfer of the Spanish ships to French control, Napoleon ordered Counter-Admiral Pierre Dumanoir le Pelley to sail to Cadiz. Le Pelley arrived at the Spanish port on 13 June in the frigates Libre and Indienne with sailors to begin manning the newly purchased ships and Commodore Julien le Ray to command them. His arrival was noted by the British blockade squadron off Cadiz under Rear-Admiral Sir James Saumarez, a veteran of the Battle of the Nile and one of Lord Nelson's famous "Band of Brothers": Le Pelley's ships were chased by HMS Superb and HMS Venerable, but the French admiral managed to evade his pursuers and reach Cadiz safely. Saumarez had been ordered to Cadiz in May 1801 with orders to blockade the Spanish fleet but also specifically to watch for an attempt by a French squadron to link with the Spanish fleet at Cadiz.

Linois sailed from Toulon on 13 June 1801 with three ships of the line and one frigate carrying 1,560 soldiers under Brigadier-General Pierre Devaux [fr]. Ganteaume's earlier expedition was still in the Eastern Mediterranean, and so the British blockade force under Sir John Borlase Warren detailed to watch Toulon was instead off Malta hoping to intercept Ganteaume on his return. Therefore, the only British ships on hand when Linois emerged from the port were a few frigates, which were easily chased away by the larger warships of the French squadron. Linois's passage was slow, facing winds from the southwest that delayed his squadron and so by 30 June, they were only off Cape de Gata in the Alboran Sea. On 1 July. they were spotted from Gibraltar although the only warship there was the 14-gun HMS Calpe under Captain George Dundas, which was unable to influence their advance. Instead, Captain Dundas ordered Lieutenant Richard Janvarin to take a boat and communicate with the Cadiz blockade force of seven ships of the line, under Saumarez.