Boleslaus I(Czech: Boleslav I. Ukrutný) (915 – 972), a member of the Přemyslid dynasty, was ruler (kníže, "duke") of the Duchy of Bohemia from 935 to his death. He is notorious for the murder of his elder brother Wenceslaus, through which he became duke. Despite his complicity in this fratricide, Boleslaus is generally respected by Czech historians as an energetic ruler who significantly strengthened the Bohemian state and expanded its territory. His accomplishments include significant economic development due to an expansion in trade, the introduction of silver mining and the minting of the first local coinage, the Prague denarius.