The Saxon Palace (Polish: pałac Saski w Warszawie) in Warsaw, Poland, was a historic architectural landmark located on Piłsudski Square in the heart of the Polish capital. Originally built in the 17th century as a noble residence, it was later expanded and transformed into a royal palace under the Saxon House of Wettin in the 18th century. The building underwent several modifications over the centuries, and is most famous for its last, 1838 design in the neoclassical style by the Polish architect Adam Idźkowski, with a distinctive colonnade.

The palace played a significant role in Polish history, serving as a military and government headquarters, including housing the Polish General Staff in the interwar period. It was also the site where the German Enigma Cipher was first broken, by Polish cryptologists in 1932. Destroyed by the Germans during the Second World War, only the section of its colonnade which has since 1925 housed the Tomb of the Unknown Soldier, has survived.

Plans for the palace’s reconstruction have been discussed since the post-war period, with various proposals put forward over the decades. In 2021, the Polish government launched an official initiative to rebuild the Saxon Palace, along with the neighboring Brühl Palace and historic tenement houses. A design competition was held in 2023, selecting the Warsaw-based architectural firm WXCA to lead the reconstruction effort. Reconstruction is expected to be completed by 2030.

Originally, the site of the Saxon Palace was occupied by the manor house of Tobiasz Morsztyn [pl]. After 1661, his brother and heir, Jan Andrzej Morsztyn, constructed a two-story baroque style palace with four towers on the site of the manor and part of the Sigismund III Embankment, which was known as the Morsztyn Palace (Polish: Pałac Morsztynów). In 1713,

In 1713 the Morsztyn Palace was purchased by the first of Poland's two Saxon kings, Augustus II the Strong (reigned in Poland 1697–1706 and 1709–33). The king first had resided in Wilanów Palace, which he had remodeled. The Warsaw Royal Castle, a Renaissance building, seemed too outdated to him. The king expanded and remodeled the palace, now called the Saxon Palace. The works were completed in 1724 and were overseen by Carl Friedrich Pöppelmann and Joachim Daniel von Jauch. The renovated palace became part of the baroque urban development of the Saxon Axis, which extended from Krakowskie Przedmieście to the Mier Barracks.

Starting in 1716, the palace's Theater Hall, along with an amphitheater in the Saxon Garden and the Royal Castle, served as a venue for theatrical performances—Warsaw did not yet have a dedicated theater building at that time. The palace's decorations were designed by Louis de Silvestre.

As part of the expansion of the complex, adjacent noble residences were incorporated. In 1721, the estate of the Sanguszko family, later known as the Brühl Palace, was added. In 1726, the residence of Bishop Teodor Andrzej Potocki was annexed and later transformed into the Blue Palace, intended for Anna Orzelska, the illegitimate daughter of Augustus II the Strong. The reconstruction of the palace and the development of the Saxon Axis took place in three phases: the first from 1713 to the early 1720s, the second until the death of Augustus II in 1733 (when financial and political constraints significantly slowed construction), and the final phase in the 1730s and 1740s, when his son king Augustus III completed the redevelopment of the complex (amongst other works two wings were added in 1748).

After the death of Augustus III of Saxony in 1763, the palace lost its status as a royal residence and fell into decline. However, it remained in the possession of successive Saxon electors, who rented out its rooms for offices and apartments.