The Battle of Oudenarde, also known as the Battle of Oudenaarde, was a major engagement of the War of the Spanish Succession, pitting an Anglo-Dutch force consisting of eighty thousand men under the command of the Duke of Marlborough, Lord Overkirk and Prince Eugene of Savoy against a French force of eighty-five thousand men under the command of the Duc de Bourgogne and the Duc de Vendôme, the battle resulting in a great victory for the Grand Alliance. The battle was fought near the city of Oudenaarde, at the time part of the Spanish Netherlands, on 11 July 1708. With this victory, the Grand Alliance ensured the fall of various French territories, giving them a significant strategic and tactical advantage during this stage of the war. The battle was fought in the later years of the war, a conflict that had come about as a result of English, Dutch and Habsburg apprehension at the possibility of a Bourbon succeeding the deceased King of Spain, Charles II, and combining their two nations and empires into one.
The engagement itself came about after a series of offensive and defensive manoeuvres between an Allied army under the command of Marlborough and a French army under the command of the Duc de Bourgogne. The two French commanders quarrelled about the direction their army should take, although roughly a month before the battle, the French army moved westwards and captured the Allied-held fortresses of Bruges and Ghent. This proved to be an unexpected and worrying action to Marlborough, who waited until Eugene had joined his army before he decided to undertake any offensive operations. The French moved to attack again, aiming to capture the city of Oudenaarde, which would cut off communication and supply routes between Marlborough and England and thus allow for a significant victory over the Grand Alliance. Marlborough managed to figure out the French plan of action, and forced marched his men towards Oudenaarde to defend it from the expected French attack. On 11 July, the two forces met near the city.
thumb| right|250px|The Duke of Marlborough at the Battle of Oudenaarde, by John Wootton.
Burgundy, making another mistake, decided to launch an attack, over protests by Vendôme. The French right wing began to attack the Allied positions near Eine, while the left wing, for unknown reasons, remained stationary near Huise. A very strong position was held by the Allied left wing. Twenty-eight cavalry squadrons protected the right flank of Cadogan's infantry, which would receive the attack, which proceeded at about 4:00 p.m.. Burgundy ordered the assault, which landed on Prussian cavalry squadrons under Dubislav Gneomar von Natzmer. Although intense fighting ensued, the attack was dispersed. Then, Vendôme made a dubious tactical decision to personally lead an attack of twelve infantry regiments, fighting hand-to-hand with a half-pike. This meant that while one commander (Burgundy) was in his headquarters with no view of the ongoing battle, the other commander was personally fighting in the field, with no possibility of directing his men. Most historians agree that had the French left wing attacked the weakened Allied right wing, it would have been forced to retreat. Vendôme realized this, asking Burgundy for permission to attack with the left wing. Burgundy sent back a messenger with a message of refusal but the messenger failed to deliver the message. The situation worsened with Vendôme believing that support would arrive for his troops, who were lengthening their line of battle and threatening to envelop the Allied left flank. As French infantry regiments approached, they lengthened the Allied line but too slowly and not great enough in extent to prevent the French from threatening the Allied positions. For unknown reasons, about half of the total forces the French had at their disposal during the battle were kept in reserve, never being called up to participate in the battle. There was a great mass of French cavalry and infantry in some raised ground north of the Norken River along with many of Burgundy's troops that remained inactive in the battle and did not advance forwards to assist their fellow Frenchmen, even when the tactical situation had turned against them with the arrival of Overkirk's Dutch troops. Many of the French cavalry squadrons had remained in reserve, mainly because of the advice that they had been given of the ground before them being impassable by their horses. Bodart gives roughly similar numbers for the French casualties (6,000 killed or wounded and 8,000 captured), but higher numbers for allied ones (6,000 killed or wounded).
On the other hand, the reputation of the Allied commanders were greatly enhanced by the victory. For Marlborough, his eye for choosing the correct ground, his sense of timing and his keen knowledge of the enemy were again amply demonstrated. Eugene's reputation was also enhanced—while Marlborough remained in overall command, Eugene had led the crucial right flank and centre. Once again the Allied commanders had co-operated remarkably well. "Prince Eugene and I," wrote the Duke, "shall never differ about our share of the laurels."