Prince Boguslaw Radziwill (1620-1669) was a Polish-Lithuanian magnate.

Owner of Bierże , Dubinki , Słuck and Kopyta . Great Chorazy of Lithuania since 1638, Koniuszy of Lithuania since 1648, Starost barski. Governor of Prussia (generalny gubernator Prus Elektorskich) since 1657. He held the title of Imperial Prince of the Holy Roman Empire.

Since several decades, the interests between Radziwłł family and the state (Polish-Lithuanian Commonwealth) begun to drift appart, as Radziwłł were less and less satisfied with the magnatial status of the family and its immense wealth and began craving for more political power.

In 1654, during the Swedish invasion of Poland, known as The Deluge, together with his cousin Janusz Radziwiłł, he began negotiations with Swedish king Charles X Gustav of Sweden, aimed at breaking the Commonwealth and the Polish-Lithuanian union. They signed a treaty according to which Radziwiłłs were to rule over two sovereign principalities carved up from the lands of the Grand Duchy of Lithuania, which were to become a Swedish protectorate.

The Swedish defeat and eventuall retreat from the territories of the Commonwealth abruptly ended the plans of Janusz and Bogusław. Their lines of the Radziwiłl family became extinct by the next generation, and their only lasting achievement was to tarnish the Radziwiłł family name for years to come, their treason eclipsing the deeds of other Radziwiłłs like Michał Kazimierz Radziwiłł, who fought for the Crown and the Commonwealth against the Swedes.