Pažaislis monastery and church (Lithuanian: Pažaislio vienuolynas ir bažnyčia, Polish: Klasztor w Pożajściu) form the largest monastery complex in Lithuania, and the most magnificent example of Italian Baroque architecture in the country. It is situated in the Petrašiūnai elderate of Kaunas, Lithuania, on a peninsula in the Kaunas Reservoir near the Kaunas Yacht Club.
Founded in 1662 by nobleman of Grand Duchy of Lithuania and Great Chancellor of Lithuania, Krzysztof Zygmunt Pac, for the Order of the Camaldolese Hermits, the main construction continued until 1674 and resumed in 1712. The monastery was designed by Pietro Puttini, Carlo and Pietro Puttini, and Giovanni Battista Frediani. Exclusive architectural solutions were used for the first time in Europe: a hexagonal church plan, and a concave facade. The interior stucco work is ascribed to Joan Merli and the frescos to Michelangelo Palloni. In 1755 the addition of the towers and the dome was funded by the king's chamberlain Michał Jan Pac.
The monastery's church, decorated with highly polished marble, was damaged by the horses of Napoleon's army which was based in the complex. In 1832 the monastery was closed by the Russian authorities and later converted into an Orthodox church. The author of the Imperial Russian national anthem God Save the Tsar, Alexei Lvov, was interred there in 1870. In 1915-1918 when the Orthodox monks had fled a German war hospital was established in the monastery. After 1920 the ruined monastery returned to Roman Catholics and was restored by sisters of the Lithuanian convent of St. Casimir. After World War II, the Soviet authorities converted the church and monastery into an archive, a psychiatric hospital and finally an art gallery (in 1966). In 1990s the complex was returned by the newly independent Lithuania to the nuns of the convent and reconstruction work began.