Marchwicki Palace in Brzeźno is a neoclassical palace located in Brzeźno, in Ostrołęka County, built for the Marchwicki family around 1900 according to a design by Leonard Marconi.

The Brzeźno estate became the property of Maciej Marchwicki in 1849.^[1] After his death in 1864, the estate passed to his son Stanisław, who commissioned the palace design from Warsaw architect Leandro Marconi. Marconi created a palace inspired by Polish classicism of the Stanisław era, particularly the palace in Natolin, as well as the architectural style of the Palace on the Isle in Łazienki Park in Warsaw.^[2] A distinctive feature directly borrowed from Natolin, which defines the character of the entire structure, is the elliptically curved grand-order columnar portico crowning an elliptical recess in the front façade that houses the palace’s entrance.^[2]

The palace is seven bays wide, two stories tall, built on a rectangular plan with two single-story annexes attached to the side walls, the eastern one supporting a balcony. On the garden side, the façade is adorned with a pentagonal risalit opening onto a terrace.^[3]

The palace is surrounded by a landscape park established around the mid-19th century.^[4]

After World War II, the palace was nationalized and handed over to the local State Agricultural Farm. It underwent renovation in 1965.^[3] Following the political transformation, the palace became the property of the State Treasury. In 2006, it was purchased by a private owner and underwent a major renovation.^[3]