Russian statesman and confidant of Tsar Alexander I, who made him a member of the Secret Committee (1801–03) for the planning of reforms. Under Alexander and his successor, Nicholas I, Novosiltsev served in the administration of Russian Poland.

Novosiltsev received his early training in the corps of pages and served in the military from 1783 to 1796. In 1803 he was named president of the St. Petersburg Academy of Sciences. Between 1804 and 1809 he served on a variety of diplomatic missions in Europe and in 1813 became the vice president of the provisional council charged with the administration of the duchy of Warsaw, in which capacity he was known for his severity toward the Poles.

He became chairman of the Council of State and the Cabinet of Ministers in 1832 and was granted the title of count in 1833.