The Royal Monastery of San Lorenzo de El Escorial (in Spanish, Real Monasterio de San Lorenzo de El Escorial) is an immense palace, Augustinian monastery, museum, and library complex located at San Lorenzo de El Escorial, a town 45 kilometres north west of Madrid in the autonomous community of Madrid in Spain. Situated next to Mount Abantos in the Sierra de Guadarrama, the construction of this monumental complex was ordered by King Philip II of Spain to commemorate the victory at the Battle of St. Quentin in 1557 over the troops of Henry II, King of France. The complex was also intended to serve as a necropolis as for the interment of the remains of Philip's parents, Charles I and Isabella of Portugal, as well as his own and his descendants, in addition to being a seat of studies in aid of the Counter-Reformation. Since then, it has been the burial site for most Spanish kings of the last five centuries, from the houses of Habsburg and Bourbon. The Royal Pantheon contains the tombs of the Holy Roman Emperor Charles V (King Charles I of Spain), Philip II, Philip III, Philip IV, Charles II, Louis I, Charles III, Charles IV, Ferdinand VII, Isabel II, Alfonso XII and Alfonso XIII. The two Bourbon kings Philip V and Ferdinand VI, as well as King Amadeo of Savoy (1870-1873), are not buried in the Monastery. The building's cornerstone was laid on April 23, 1563. The construction was overseen by Juan Bautista de Toledo, who did not live to see its completion, dying in 1567, and direction passed to his apprentice Juan de Herrera, under whom it was completed in 1584.

The floor plan of the building evokes a grill shape, which traditionally was thought to have been done in honor of Saint Lawrence, who was martyred by being roasted to death on a grill. St. Lawrence's feastday is August 10, which is the same date on which the aforementioned Battle of St. Quentin took place. In reality, however, the architectural origin of the building's shape is quite controversial. Aside from the happy coincidence of the grill shape, which did not even appear until Herrera eliminated the six interior towers of the facade, the floor plan appears to be more nearly based on the descriptions of the Temple of Solomon by the Judeo-Roman historian Flavius Josephus, modified as necessary for the building's function as a monastery and for the various other purposes Philip II intended the edifice to serve, including pantheon, basilica, convent, school, library, and palace. All these factors resulted in the building doubling its initial size.

The statues of David and Solomon that flank the entrance to the church serve as a reminder of this origin and parallel the differences between the warrior Charles V and the prudent Philip II. In the same way, the fresco of Solomon, situated in the centre of the library, shows Solomon's great wisdom in the famous episode with the Queen of Sheba.

The complex has an enormous store of art, including masterworks by Titian, Tintoretto, El Greco, Velázquez, Roger van der Weyden, Paolo Veronese, Alonso Cano, José de Ribera, Claudio Coello and others. Also at the complex is a library containing thousands of priceless ancient manuscripts like the collection of the Moroccan sultan Zidan Abu Maali (r.1603–1627). Giambattista Castello designed the main staircase. On November 2, 1984, UNESCO declared The Royal Site of San Lorenzo of El Escorial a World Heritage Site. It is an extremely popular tourist attraction, often visited as a day trip from Madrid.