Nesvizh Castle or Niasvizh Castle is a residential castle of the Radziwiłł family in Nesvizh, Belarus. The estate was owned by the Radziwiłł magnate family from 1533, when it was awarded to Mikołaj Radziwiłł and his brother Jan Radziwiłł after the extinction of the Kiszka family family. Since the Radziwills were one of the most important and wealthy clans of the Grand Duchy of Lithuania, it was there that the Lithuanian Archive was moved in 1551. In 1586 the estate was turned into an ordynacja.
In 1582 Mikołaj Krzysztof "Sierotka" Radziwiłł, the Marshal of Lithuania, voivode of Trakai and Vilnius and castellan of Šiauliai, started the construction of an imposing square three-storey chateau. Although the works were based on a pre-existing structure of a mediæval castle, the former fortifications were entirely turned into a renaissance-baroque house. Construction was completed by 1604, and they added several galleries half a century later. The château's corners were fortified with four octagonal towers.
In 1706, during the Great Northern War, Charles XII's army sacked the castle and destroyed its fortifications. Several decades later, the Radziwiłłs invited some German and Italian architects to substantially renovate and enlarge the chateau. Antoni Zaleski decorated its yellow facades with baroque stucco work. The 16th-century castle gates were also reconstructed, and the two-storey gatehouse tower was crowned with a helm. It was at this time that the three separate buildings surrounding the central courtyard were joined into a single structure.
The most important structure in Nesvizh is the Corpus Christi Church (picture) (1587 to 1603), connected with the castle by a dam over a ditch and containing coffins of 72 members of the Radziwill family, each interred in a simple coffin made of birch and marked with Trąby Coat of Arms. Designed by the Italian architect Gian Maria Bernardoni (1541 to 1605), the church is considered the first Jesuit temple patterned after Il Gesù in Rome, the first domed basilica with Baroque facade in the World
and the first baroque piece of architecture in Eastern Europe
. In 1939, the Radziwiłł family was expelled from the castle by the invading Red Army. In Soviet times, the chateau was used a sanatorium, while the park gradually fell in neglect. In 1994, the castle complex was designated the national historical and cultural reserve. Twelve years later, the castle complex was inscribed on the World Heritage List.