Mikołaj Krzysztof Radziwiłł (4 February 1515 – 28 May 1565), nicknamed The Black (Polish: Czarny), was a Polish-Lithuanian noble who held several administrative positions within the Grand Duchy of Lithuania: Voivode of Vilnius, Grand Lithuanian Chancellor, and Grand Hetman of Lithuania. Alternate renditions of his name include , , and . His first name is sometimes given in English as Nicholas. Political influence Mikołaj was able to gain much political influence thanks to the romance between his cousin Barbara Radziwiłł and the King of Poland and Grand Duke of Lithuania Zygmunt II August. This made him one of the most powerful royal advisers. Mikolaj became Marshal of Lithuania, Grand Chancellor of Lithuania, as well as Palatine of Vilnius, gained immense wealth and became the most powerful magnate in the Commonwealth of that time. The growing influence of the Radziwiłł family was further bolstered when, during a diplomatic mission to Charles V and Ferdinand I, he and his cousin Mikołaj the Red received a hereditary title of Prince (Reichsfürst (SRI)). He formed an alliance with his cousin Mikołaj "the Red" Radziwiłł against other notable Lithuanian families in the rivalry for the dominant status in the Great Duchy of Lithuania. This alliance marked the formation of a dynastic-like cooperation between Radziwiłłs and showed how family interests could affect magnates' relations with the state. Both Radziwiłłs backed the cause of Lithuania's sovereignty and opposed the growing Polish-Lithuanian union. Coincidentally, despite opposing close ties with Poland, he was the chief negotiator in the successful negotiation between the Grand Duchy of Lithuania and the state controlled by the Livonian Order, which led to the secularisation of Livonia and its union with the Grand Duchy of Lithuania in 1562. Mikołaj contributed to the ongoing Polonisation of the Grand Duchy, influencing other Lithuanian nobles to follow him in adopting Polish cultureits fashion, customs and language. Despite being a fervent opponent of the closer union with Poland, he was an active supporter of Polish culture in Lithuania. He himself did not speak Lithuanian, his knowledge of Ruthenian, at that time the official language of the Grand Duchy, was limited. Polish was his native language and the only one he was able to use fluently. Religious activities He was known for his religious beliefs, as he was one of the most prominent converts and advocates of the Reformed churches faith in Grand Duchy of Lithuania. He provided financial support