The Royal Baths Park (Polish: Park Lazienkowski, or Lazienki Krolewskie) is the largest park in Warsaw.
It was established in the 17th century by Tylman van Gameren, in the baroque style, for Stanislaw Herakliusz Lubomirski. It took the name Lazienki ("Baths") from a bathing pavilion that was located there. In 1764 the gardens were acquired, after his election as King of Poland, by Stanislaw August Poniatowski.

The now classicist-style gardens became Stanislaw August's life work. The park was designed by Dominik Merlini, Johann Christian Kammsetzer and landscape gardener Jan Christian Schuch. The park's principal buildings are clustered around or near the Lazienki Lake and Łazienki River. Stanislaw August's palace, placed on the lake, is called a "Palace on the Water."

Most of the park's buildings burned during and after the Warsaw Uprising (1944), amid fighting among German, Polish and Soviet forces. The structures nevertheless were relatively well-preserved, compared to Warsaw's Old Town, and the park's reconstruction was completed within a few years after the war.