FEDERICO GUGLIELMO IV, king of PRUSSIA. - B. on 15 Oct. 1795 in Berlin; d. on 2 Jan. 1861 at Sans-Souci. Succeeding his father Federico Guglielmo III in 1840, he sought to eliminate conflicts with the Holy See. He therefore permitted the archbishop of Gnesna and Posnania, Dunin, to return to his diocese and sent Count Brühl to Rome to put an end to the dispute concerning the see of Cologne, where the person of Droste-Vischering was unwelcome to the sovereign: the difficulties were overcome through the appointment of Geissel as coadjutor.
During the crisis of 1848-49 he refused the German imperial crown offered to him by the Frankfurt Parliament, because he did not wish to oppose Francesco Giuseppe and because he was accepting the crown from a democratic assembly (28 March 1849). Subsequently, relations between the State and the Catholic Church again became difficult because of provisions issued by the Minister for Religious Affairs, Raumer. On the whole, however, the situation of Catholics in the Kingdom of Prussia, under the reign of F. G. IV, showed an improvement over the treatment inflicted upon them by his father. In 1858 the sovereign, suffering from cerebral softening, appointed his brother Guglielmo as regent.