Abstract: This article examines the nature of relations between Muslims and Christians in southern Italy during the thirteenth century. In response to uprisings in Sicily, the emperor Frederick II transferred an estimated 20,000 Muslims to the city of Lucera in Apulia. Outside the Iberian Peninsula, Lucera came to have the largest Muslim population of any city in western Europe. Although the formation of the colony led to competition for resources between its inhabitants and the local Christian population, the members of the two religious communities often traded and collaborated. Social mobility was possible for the Lucerine Muslims, particularly through military service. Like Christians and Jews living in the dar al-Islam, the Muslims of Lucera had a protected status, and they paid a tax called the jizya. They remained free to practice their religion. The heavy taxes paid by the Muslim colony at Lucera during its almost eighty-year existence made it a valuable asset to the Hohenstaufen and Angevin crowns. Nevertheless, the settlement was dismantled in 1300 on the order of the Angevin king, Charles II, who gave a religious justification. The colony's history provides insight into the complex relations between Muslims and Christians in medieval Mediterranean Europe.