Nicolaus or Mikołaj Szyszkowski (1590–1643) of Clan Ostoja was a Prince-bishop of Warmia from 1633 until his death in 1643. Born around 1590, he was the son of Jan and Anna z Ujejskich. He began his studies (in the fields of theology and philosophy) in Braniewo (Braunsberg), and continued them abroad, in Rome. He received the Holy Orders from his relative, Prince of Sieradz and bishop of Płock, Marcin Szyszkowski, and also because of his relative he got holdings ('beneficja') in Czerwińsk (where he was an abbot) and elsewhere. In the royal court of the Polish king Sigismund III Vasa he achieved the official rank of Great Secretary, and it was then that he became a colleague of Stefan Sadorski. After the death of his relative, bishop Marcin (who in time advanced from the position of Bishop