Guelphs, the designation of a powerful party in the middle ages, which, in Germany, and at a later period in Italy, opposed the German emperors and their adherents, who were called Ghibellins. The wars of the Guelfs and Ghibellins became the struggle between the spiritual and secular power—the Guelphs standing for the Pope, and the Ghibellins for the Emperor. These factions filled Italy with bloodshed for nearly 300 years.

The rise of the Guelphs is referred by some to the time of Conrad III., in the twelfth century; by others to that of Frederick II.; and by others, again, to that of his successor, Frederick III., in the thirteenth century. The name of Guelph is commonly said to have been formed from Welfe, or Welfo. The Emperor Conrad III., having taken the duchy of Bavaria from Welfe VI., brother of Henry, Duke of Bavaria, Welfe, assisted by the forces of Roger king of Sicily, made war on Conrad, and thus gave birth to the faction of the Guelphs. Some derive the name Guelph from the German Wolf; and others deduce it from the name of a German called Guelfe, who lived at Pistoia; adding, that his brother, named Gibel or Ghibel, gave his name to the Ghibellins. See Ghibellins.