Simon de Montfort, 5th Earl of Leicester, known as Simon IV de Montfort and as Simon de Montfort the Elder, was a French nobleman and knight of the early 13th century. He is widely regarded as one of the great military commanders of the Middle Ages. He took part in the Fourth Crusade and was one of the prominent figures of the Albigensian Crusade. Montfort is mostly noted for his campaigns in the latter, notably for his triumph at Muret. He died at the Siege of Toulouse in 1218. He was Seigneur of Montfort from 1188 to his death and Earl of Leicester in England from 1204. He was also Viscount of Albi, Béziers and Carcassonne from 1213, as well as Count of Toulouse from 1215.

The Fourth Crusade (1202–1204) was a Latin Christian armed expedition called by Pope Innocent III. The stated intent of the expedition was to recapture the Muslim-controlled city of Jerusalem, by first defeating the powerful Egyptian Ayyubid Sultanate. However, a sequence of economic and political events culminated in the Crusader army's 1202 siege of Zara and the 1204 sack of Constantinople, rather than the conquest of Egypt as originally planned. This led to the Partitio terrarum imperii Romaniae or the partition of the Byzantine Empire by the Crusaders and their Venetian allies leading to a period known as Frankokratia, or "Rule of the Franks" in Greek.