Stanisław of Masovia

He was the eldest son of Konrad III the Red and his third wife Anna, a daughter of Mikolaj Radziwiłł the Old, Voivod of Vilnius and the first Grand Chancellor of Lithuania.

After the death of their father on 28 October 1503, Stanisław and his younger brother Janusz III inherited his domains but, because they were minors, remained under the regency of their mother.

In the same year when they attained their majority, both princes attended the wedding of King Sigismund I the Old to Bona Sforza in Kraków.

The main suspect was a Płock lady called Katarzyna Radziejowska, who after being seduced and abandoned by both princes, was believed to have poisoned firstly Anna Radziwiłł, then Stanisław and finally Janusz III in revenge.

Declared guilty, she and her supposed accomplice were tied naked to poles and beaten for hours, and finally burned alive.