The time when the struggle between Christian Europe and the Islamic world was most intense, and hostility reached its peak, was the Crusades, which lasted two centuries. In The Christian West a thought was dominant and spread that the Crusades cannot be successful in the issue of converting Muslims into Christians through war but through missionaries. As a result, from the 12th century, which was accepted as the beginning of Orientalism or as a major turning point in Orientalism, missionaries who had information about the Quran, prophets, and Islamic culture were sent to Muslim lands. Some of them wrote some works on the Prophet and Islam and they were a determinant of Europeans opinion on Islam. This article briefly reviews the life of William of Tripoli, who lived in Islamic geography for a long time, and introduces his two works, Notitia de Machometo and De statu Sarracenorum, about the Prophet and Islam. In addition, some of his views on Islam and Muslims will be discussed. Because William of Tripoli is an effective author in forming the image of prophets and Islam, in the West in the Middle Ages and later.