At the Battle of Muret on 12 September 1213 the Crusading army of Simon IV de Montfort defeated the Catharist, Aragonese and Catalan forces of Peter II of Aragon, at Muret near Toulouse.

Simon IV de Montfort was the leader of the Albigensian Crusade to destroy the Cathar heresy and incidentally to join the Languedoc to the crown of France. He invaded Toulouse and exiled its count, Raymond VI. Count Raymond sought assistance from his brother-in-law, King Peter II of Aragon, who felt threatened by Montfort's conquests in Languedoc. He decided to cross the Pyrenees and deal with Montfort at Muret.

On 10 September, Peter's army arrived at Muret, and was joined by a Toulousain militia. He chose to position his army so their right flank was protected by the Saudrune River, and the left protected by a marsh. He left the Toulousain militia to assault the walls of the city.

Simon de Montfort led an army of 870 French Crusaders, along with a small contingent of knights brought by his ally, the viscount of Corbeil. Simon de Montfort's 870 mailed cavalry included 270 knights, making the small force of exceptional quality. King Peter of Aragon had brought 800 to 1,000 Aragonese cavalry, joined by a militia from Toulouse and armies brought by the counts of Comminges and Foix. King Peter of Aragon's combined forces possibly numbered 4000 cavalry, with thirty to forty thousand infantry.

Coordinates: 43°27′40″N 1°19′36″E / 43.4611°N 1.3267°E / 43.4611; 1.3267

Muret (French pronunciation: [my.ʁɛ] ; in Occitan Murèth) is a commune in the Haute-Garonne department in southwestern France.

It is an outer suburb of the city of Toulouse, even though it does not belong to Greater Toulouse, which it has declined to join. It lies southwest of Toulouse and is the largest component of the intercommunality of Muretain.

On September 12, 1213 the Battle of Muret took place between Simon de Montfort and a coalition force under the control of Count Raymond of Toulouse, and King Pedro II of Aragon.

De Montfort had been fighting Albigensian heretics during the Albigensian Crusade, when he was besieged by the vastly superior coalition forces. Refusing to surrender or be starved into submission, de Montfort went instead on the offensive. Leading his knights out of the town, he proceeded to disperse them into a wide arc before falling upon the Toulouse cavalry with a noise like a whole forest going down under the axe. Next to fall victim to such arcing tactics was the Aragonian cavalry where King Pedro himself fell to the sword. After this, all that was left was to scatter the remaining cavalry defending the coalition camp before falling upon the infantry besieging Muret's walls. Despite overwhelming numbers,the coalition army numbering almost 34, 000 men and de Montfort's army only 2 100, the siege of Muret was lifted.