Guelphs and Ghibellines, names of two political factions in northern and central Italy from about the 12th to the 15th century. These factions originated in the early 12th century in Germany as the partisans of a struggle for the throne of the Holy Roman Empire between two princely houses, the Welfs, who were the dukes of Saxony and Bavaria, and the Hohenstaufens, the rulers of Swabia. In the early 13th century, when the Welf Otto of Brunswick was involved in a contest for the imperial crown with Frederick II of Hohenstaufen, the struggle between the German factions moved to Italy. The name Guelph was a corruption of Welf; Ghibelline was a corruption of Waiblingen, an estate belonging to the Hohenstaufen emperors.

In the course of the 13th century, the names of the two groups lost their original German significance. The Guelphs became the party opposing the authority of the Holy Roman emperors in Italy and supporting the power of the papacy, while the Ghibellines supported the imperial authority. The Guelph Party, moreover, became a nationalist party in a sense, for it enlisted itself in support of the Italian principalities and city republics that were demanding provincial or municipal rights and liberties.

Medieval Italy was disrupted by the violent political and military conflicts between the partisans of the two great factions. In general, the great noble families adhered to the Ghibellines, and the great cities supported the Guelphs. Eventually the division became more geographical. The nobles in the more northern districts inclined toward the Ghibellines and those in the central district toward the Guelphs. Pisa, Verona, and Arezzo were Ghibelline strongholds; Bologna, Milan, and, particularly, Florence supported the Guelphs. In Florence struggles between the parties resulted in civil war that raged for more than ten years, until, in 1266, the Ghibellines were expelled from the city.

In the 14th century, after the emperors had ceased to be a major power in Italy, the contest degenerated into a struggle of local political factions availing themselves of the prestige of ancient names and traditional or hereditary prejudices. In 1334 Pope Benedict XII forbade, under pain of the censures of the church, the further use of the Guelph and Ghibelline names, but they were sometimes applied to different factions as late as the 16th century.