The House of Radziwiłł (Polish pronunciation: [raˈd͡ʑiviww]; Lithuanian: Radvila; Belarusian: Радзівіл, romanized: Radzivił; German: Radziwill) is a Polish princely family of Lithuanian origin, and one of the most powerful magnate families originating from the Grand Duchy of Lithuania and later also prominent in the Crown of the Kingdom of Poland.

The family produced many individuals notable in Lithuanian, Polish, Belarusian, German as well as general European history and culture.

[7] Its first notable member, Kristinas Astikas (born 1363), a close associate of the Lithuanian ruler Vytautas, became Castellan of Vilnius.

[9] The Polish forms Radziwiłł or Radźwił (patronymics Radziwiłłowic(z), Radźwiłowic(z)) may come from the originally Belarusian Radzivil, i.e. a derivative of il from the base Radziv-, derived from a shortened form of the name Radzivón (with a v removing the hiatus from the church Rodi.ón, similarly to Larivón from Lari.ón (Ilarión) or Ljavónt from (Le.ón), and similarly to Stanil from Stanislav.

The Biržai-Dubingiai line was moderately more successful and produced some very notable state officials and politicians, but it also became extinct after Ludwika Karolina Radziwiłł's death in 1695.

In 1518, Holy Roman Emperor Maximilian I created Mikalojus Radvila's son, Mikołaj, Reichsfürst ("Imperial Prince") of Goniądz and Meteliai after the Jagiellonian-Habsburg congress at Vienna.

Some members of the Nesvizh–Kletsk-Olyka branch of family remained as Calvinists for two generations until the children of Mikołaj "the Black" converted to Roman Catholicism before the end of the century.

[16] Queen Barbara Radziwiłł, sister of Mikołaj "the Red" and first cousin of Mikołaj "the Black", was practicing catholic[17] and hence, despite controversy surrounding her secret wedding with the King, she was recognized by popes Paul III and Julius III as legitimate royal wife and Queen of Poland.

Its importance is manifested by family relations with such famous nobility dynasties in Belarus, Ukraine, Poland, the Great Duchy of Lithuania, Samogitia, and Rus like Zaslawski, Rohatinski, Lukomski, and Olshanski-Dobrowicki.

The significance of the Radziwiłł family is proved by the marriage of Anna to Konrad III Rudy, duke of Masovia, who owned the largest Polish principality.

In 1547 Barbara Radziwiłł was married in secret to Sigismund II Augustus, thus legally becoming royal consort; she was officially proclaimed Queen of Poland and Grand Duchess of Lithuania the next year.

[22] Although the marriage caused scandal within the country as it was performed without informing Polish nobles, the royal couple was supported by Papal Curia,[23] as well by the Radziwiłł family's ally and the King's former father-in-law, Ferdinand Habsburg.

In 1583 bishop Jerzy Radziwiłł was elevated to the cardinalate by Pope Gregory XIII, established a closer relationship with the influential noble banking families Altoviti and Strozzi.

During this time until the first half of the 17th century, the Radziwiłłs were the most influential and richest family among the magnate dynasties of the Grand Duchy of Lithuania.

In the 18th century, the army of Hieronim Florian, for instance, had 6,000 men and was equal to the entire armed forces of the Grand Duchy of Lithuania.

Members of the Radziwiłł family held important state posts in the Rzeczpospolita and in the Grand Duchy of Lithuania.

8 chancellors, 7 hetmans, 15 castellans, 19 marszałeks, and 19 voivodes, almost exclusively representing the Grand Duchy of Lithuania, rather than the Crown, belonged to the dynasty.

Karol Stanisław Radziwiłł (1734–1790) of the Nieśwież line was the wealthiest magnate in Poland, in the second half of the 18th century, and one of the richest men in Europe.

During the Great Sejm from 1788 until he died in 1790, he was a leading opponent of reform and King Stanisław II Augustus and his allies, the members of the so-called Familia political party headed by the Czartoryski family.

After the three partitions of the Polish–Lithuanian Commonwealth in the late 18th century, towns and estates owned by the Radziwiłłs became parts of territories that belonged to Russia, Prussia and Austria.

In 1959, Janusz's third son prince Stanisław Albrecht Radziwiłł married Caroline Bouvier, the younger sister of First Lady Jacqueline Kennedy.

[28] Another property Antoni Radziwiłł owned in Prussian-Poland was Antonin, a hunting lodge he had built between 1822 and 1824 by the German architect Karl Friedrich Schinkel, named after him.

Later in his life, Antoni Radziwiłł moved permanently to Antonin with his wife, Louise of Prussia, and two daughters Wanda and Eliza.

Antoni Radziwiłł was a well-connected composer among European musical circles and with time transformed the Antonin property into a popular musical salon among greatest talents of the area such as Niccolò Paganini, Johann Wolfgang von Goethe, Frédéric Chopin and Ludwig van Beethoven.

However, due to the activities of Janusz Radziwiłł during The Deluge, a series of mid-17th-century campaigns in the Polish–Lithuanian Commonwealth, the family lost much of its wealth and power.

However, during Janusz Radziwiłł's lifetime, the interests between his family and the Polish Crown began to drift apart, as the Radziwiłłs sought to increase their wealth and power, safeguard Protestantism and support ethnically Lithuanian culture, which caused him to join the opposition against King Sigismund III Vasa in 1606.

Depending on the importance and size of owned lands, they were called either principalities (Nesvizh, Olyka, Biržai, Dubingiai, Kapyl, Slutsk, Staryi Chortoryisk, Stary Zbaraz, Goniądz and Medele), counties (Mir, Biała Podlaska, Dzyarzhynsk, Kopys, Zabłudów, Kėdainiai, Zolkow, Pomorzani, Belykamen, Kražiai), or estates (Nevel, Krasnoye, Sebezh, Musninkai, Sereya, Horodok, Sobolew, Slovatichi, Ruchai, Kolki, Vyazyn, Rafałówka, Zhmigrod, Beloozero, Yampol, Shumsk, Sverzhen, Drisvyaty, Naliboki).

[30] The family ties to the banking dynasties Altoviti and Strozzi played an important role to secure titles and wealth with the Roman Curia.

This, however, cost the new owner, Antoni Radziwiłł, some diplomatic effort at the Congress of Vienna, as his cousin Dominik had fought in the Polish Legion on Napoleons' side, and Alexander I of Russia had therefore confiscated his whole property.

In this way, all three Radziwiłł ordynats ended up in the possession of one line, represented by the sons of Michal Hieronim, Ludwik Mikolaj of Kletsk and Antoni Henryk of Nesvizh and Olyka.