Julian Ursyn Niemcewicz (Skoki, near Brest, 6 February 1758 – 21 May 1841, Paris) was a Polish poet, playwright and statesman. He was a leading advocate for the Constitution of 3 May 1791.

Niemcewicz, scion of a moderately well-to-do Polish noble family, graduated from the Warsaw Corps of Cadets.

He subsequently served as aide to Adam Kazimierz Czartoryski and visited France, England and Italy.

Niemcewicz served as a deputy to the Great Sejm of 1788–92 and was an active member of the Patriotic Party that pushed through adoption of the historic Constitution of 3 May 1791. He was subsequently a founder of the Friends of the Constitution, formed to support the implementation of that progressive document.

After the victory of the Targowica Confederation in 1792 and the consequent overthrow of the May 3 Constitution, Niemcewicz, along with other Patriotic Party members, emigrated to Germany.

During the Kościuszko Uprising (1795), Niemcewicz served as aide to Tadeusz Kościuszko. Both were captured by the Russians at the Battle of Maciejowice (1794) and imprisoned in the Peter and Paul Fortress at St. Petersburg along with Niemcewicz's aide-de-camp named Kuźniewski. In 1796, on the death of Tsaritsa Catherine the Great, they were released by Tsar Paul I and made their way together to the United States, where in 1800 Niemcewicz married Mrs. Livingston Kean, widow of John Kean, a delegate from South Carolina to the Continental Congress.

Niemcewicz was upset when Kościuszko decamped for Europe without giving him any notice.

After Napoleon's 1807 invasion of Poland, Niemcewicz returned to Warsaw and was made secretary of the senate. After the Congress of Vienna, he was secretary of state and president of the constitutional committee in Poland.

On 11 May 1830 he unveiled a new landmark before the Staszic Palace, the seat of the Society of Friends of Science in Warsaw — a monument to Nicolaus Copernicus sculpted by Bertel Thorvaldsen.

During the failed November Uprising of 1830–31, Niemcewicz was a member of the insurrectionary Polish government. When the Russians suppressed the uprising, Niemcewicz was again forced into exile.

He died in 1841 in Paris.

Writing

As a writer, Niemcewicz tried many styles of composition. His political comedy, The Return of the Deputy (1790), enjoyed great acclaim. His novel, John of Tenczyn (1825), written in the style of Sir Walter Scott, gives a vigorous picture of old Poland.

He also wrote a History of the Reign of Sigismund III (3 volumes, 1819) and a collection of memoirs for ancient Polish history (6 volumes, 1822–23).

Niemcewicz's 1817 pamphlet Rok 3333 czyli sen niesłychany (The Year 3333, or an Incredible Dream), first published posthumously in 1858, describes a Poland transformed into a sinister Judeo-Polonia. The pamphlet has been described as "the first Polish work to develop on a large scale the concept of an organized Jewish conspiracy directly threatening the existing social structure."

His collected works were published in 47 volumes at Leipzig in 1838-40.

Works

• Władysław pod Warną (Władysław at Varna, 1788)
• Kazimierz Wielki (Kazimierz the Great, 1792)
• Powrót posła (The Return of the Deputy, 1791)
• Na hersztów targowieckich (The Targowica Chiefs)
• Podróże historyczne po ziemiach polskich (Historic Travels over the Polish Lands)
• Śpiewy historyczne (Historic Songs)
• Dzieje panowania Zygmunta III (A History of the Reign of Zygmunt III)