Dr. Nicasius de Sille (1543–1600) was a 16th-century statesman from what is now Belgium who served as a special ambassador of the Dutch Republic to several nations, and as secretary to future-Holy Roman Emperor Matthias.
Nicasius was born August 3, 1543, in the city of Mechelen, Habsburg Netherlands, the son of Nicolaas de Sille and Barbara van der Goes.
[1] He spent his early life studying, eventually becoming a Doctor Juris and practicing at the Superior Court of Mechelen.
[1] After the fall of the Southern Provinces, de Sille removed to Holland where he became pensionary of Amsterdam while maintaining his duties as secretary.
In 1584, de Sille made up the conditions of homage of Prince William to negotiate with the Earl of Leicester pertaining to control of the Habsburg Netherlands.