Bretislav (b. between 1005-1012, d. January 1, 1055) of the house of Premyslids was a duke of Bohemia from 1035 till 1055.
Břetislav was a son of duke Oldřich, then the protector of the Žatecko province, and his would-be wife Božena. In 1019 at Schweinfurt he kidnapped his future wife Jitka, a daughter of a Bavarian margrave, Andreas of Nordgau.
During his father’s reign, in 1029, he took back Moravia from Poland. About 1031 Břetislav invaded Hungary in order to prevent its expansion under king Stephen. The partition of Bohemia between Oldřich and his brother Jaromir in 1034 was probably the reason why Břetislav fled beyond Bohemian border only to come back to take the throne after Jaromir’s abdication.
In 1035 Břetislav helped Emperor Conrad II in his war against the Lusatians. In 1038 or 1039 he invaded Poland proper and sacked its capital, Gniezno, bringing the relics of St Adalbert back with him. On the way back he conquered part of Silesia including Wrocław. His main goal was to set up an archbishopric see in Prague and create a large state subject only to the Holy Roman Empire.
He was the author of decrees concerning the rules of Christianization, which included a ban on polygamy or trade on holidays.
Břetislav died in 1055 during his preparation for another invasion of Hungary.