The Guelphs and Ghibellines were factions supporting the Pope (Guelphs) and the Holy Roman emperor (Ghibellines) in the Italian city-states of Central and Northern Italy during the Middle Ages. During the 12th and 13th centuries, rivalry between these two parties dominated political life across Italy. The struggle for power between the Papacy and the Holy Roman Empire arose with the Investiture Controversy, which began in 1075 and ended with the Concordat of Worms in 1122.