Janusz Radziwiłł (1579–1620)

Janusz Radziwiłł ( _lt. Jonušas Radvila, 2 July 1579–3 December 1620) was a noble and magnate of the Polish–Lithuanian Commonwealth. He was the podczaszy of Lithuania since 1599, the castellan of Vilnius since 1619, and the starost of Borysów. Radziwiłł also held the title of "Reichsfürst" (Imperial Prince) of the Holy Roman Empire.

Radziwiłł expanded the already immense Radziwiłł family fortune through his first marriage to Zofia Olelkowicz Słucka on 1 October 1600, who, at her deathbed in 1612, left him a large estate, including seven castles and palaces and some thirty-two villages. She was canonized by the Belarusian Orthodox Church as saint "Sofia of Slutsk" thanks to her charity and miracles on the grave. His second marriage was to Elisabeth Sofie of Brandenburg, daughter of John George, Elector of Brandenburg, on 27 March 1613 in Berlin.

It was during Radziwiłł's life that the interests between his family and the state began to drift apart, as the Radziwiłłs sought to increase their wealth and power, safeguard Protestantism and support ethnically Lithuanian culture, while disregarding the public good and putting their dynastic interests over interests of the state.

Just like his father, Radziwiłł took part in a military campaign against Sweden in Livonia. Unhappy with the lack of material rewards resulting from his involvement in that campaign, however, he voiced his opposition against King Sigismund III Vasa by joining in Zebrzydowski's Rokosz in 1606 and becoming one of its leaders. This "confederatio", an armed and legal rebellion, was aimed at stopping the king's plans of strengthening his dynasty and powers by introducing hereditary monarchy, collecting additional taxes, and creating a larger standing army.