Fieschi (singular Fiesco), one of the four principal families of Genoa and its territory, said to be of Bavarian origin. The Fieschi and Grimaldis adhered to the Guelphs. the Dorias and Spinolas to the Ghibellines. Their rivalries occasioned frequent wars in the republic of Genoa between the 11th and 16th centuries, when the failure of the conspiracy against the Dorias drove the elder branch of the Fieschi into France, and left the younger poor and powerless. They defied the authority of the city in an obstinate struggle in the early part of the 12th century, but finally their castles were captured and destroyed, and they submitted. In 1150 the republic granted them the privilege of erecting a palace in Genoa; and in 1191 they resigned to the republic their castle of Lavagna and their other fiefs, in return for which they received the right of citizenship and nobility. The Fieschi family has produced two popes, Innocent IV. and Adrian V.. and a large number of cardinals, patriarchs, archbishops, and bishops, besides statesmen and warriors. (See Fiesco.)