[4] He received Saint-Gilles with the title of "count" from his father and displaced his niece Philippa, Duchess of Aquitaine, his brother William IV's daughter, in 1094 from inheriting Toulouse.

Raymond was deeply religious, and wished to die in the Holy Land, and so when the call was raised for the First Crusade, he was one of the first to take the cross.

He is sometimes called "the one-eyed" (monoculus in Latin) after a rumour that he had lost an eye in a scuffle with the doorkeeper of the Church of the Holy Sepulchre during an earlier pilgrimage to Jerusalem.

[3] The oldest and the richest of the crusaders, Raymond left Toulouse at the end of October 1096, with a large company that included his wife Elvira of Castile, his infant son (who would die on the journey) and Adhemar, bishop of Le Puy, the papal legate.

[4] The crusaders heard a rumour that Antioch had been deserted by the Seljuk Turks, so Raymond sent his army ahead to occupy it, offending Bohemond of Taranto who wanted the city for himself.

He was ill during the second siege of Antioch by Kerbogha which culminated in a controversial rediscovery of the Holy Lance by a monk named Peter Bartholomew.

The Lance itself became a valuable relic among Raymond's followers, despite Adhemar of Le Puy's skepticism and Bohemond's disbelief and occasional mockery.

Many of the minor knights and foot soldiers preferred to continue their march to Jerusalem, and they convinced Raymond to lead them there in the autumn of 1098.

Raymond led them out to besiege Maarat al-Numan, although he left a small detachment of his troops in Antioch, where Bohemond also remained.

Although he successfully captured Hisn al-Akrad, a fortress that would later become the important Krak des Chevaliers, his insistence on taking Tripoli delayed the march to Jerusalem, and he lost much of the support he had gained after Antioch.

He immediately broke his promise, attacking and capturing Tartus, and began to build a castle on the Mons Peregrinus ("Pilgrim's Mountain") which would help in his siege of Tripoli.

The qadi of Tripoli, Fakhr al-Mulk ibn Ammar, led an attack on Mons Peregrinus in September 1104 and set a wing of the citadel on fire.

William was deposed in the same year by Raymond's eldest son Bertrand, and the county remained in the possession of the counts of Toulouse throughout the 12th century.