Mansjonaria tenement house, Historical tenement house in Warsaw Old Town, Poland

The Mansjonaria tenement house stands in Warsaw Old Town on Świętojańska Street 2, displaying features from different periods of its long history. The building features a rusticated stone portal with crossed arrows on its keystone, while the overall structure comprises several interconnected sections.

The property belonged to the Mazovian dukes before Anna Holszańska gave it in 1433 to the Mansionist priests, who served her chapel in St John's Collegiate Church. A brick house stood here before 1478, and Duke Stanisław of Mazovia died in it in 1524. Baroque rebuilding in 1688 added the rusticated portal with crossed arrows; Władysław Kościelski had it rebuilt in 1918–1921, and it was reconstructed in 1950–1953.

The name Mansjonaria comes from the Mansionists, a community of priests who lived and worked here serving the nearby Collegiate Church. The building reflects this special connection through its layout and purpose, which shaped how people used the spaces for centuries.

The building now houses offices of the State Enterprise for Construction and Monumental Architecture Works, so it is not open to the public. It stands at the corner of Świętojańska Street and Castle Square, with its five-axis front façade facing the street. The three buttresses on the southern elevation, added in the 19th century because of the marshy ground, are visible from the square.

During the 1944 Warsaw Uprising the roof burned completely, yet the solid stone walls withstood the damage and allowed for full reconstruction later. This resilience of the masonry made the building one of few damaged structures in the Old Town that could actually be restored.