Nicholas Duchnowski (Polish: link=no|Mikołaj Duchnowski; 12 December 1733 – 25 June 1805) was a bishop of the Ruthenian Uniate Church, Bishop of Suprasl and all unites in New East Prussia.
After the death of Theodosius Wislocki, Nicholas Duchnowski was selected locum tenens bishop of Suprasl until he was consecrated in 1804.