The Palazzo Spada is a palace in Rome that houses a grand art collection, the Galleria Spada. The collection was originally assembled by Cardinal Bernardino Spada in the 17th century and added to by his grandnephew Cardinal Fabrizio Spada (1643-1717), and by Virginio Spada (1596-1662). The palace is located in the rione Regola, at Piazza Capo di Ferro, 13, with a garden facing the Tiber, very close to the Palazzo Farnese.

It was originally built in 1540 for Cardinal Girolamo Capodiferro. Bartolomeo Baronino, of Casale Monferrato, was the architect, while Giulio Mazzoni and a team provided lavish stuccowork inside and out. The palazzo was purchased by Cardinal Spada in 1632. He commissioned Francesco Borromini to modify it for him, and it was Borromini who created the masterpiece of trompe-l'oeil false perspective in the arcaded courtyard, in which diminishing rows of columns and a rising floor create the optical illusion of a gallery 37 meters long (it is 8 meters) with a lifesize sculpture in daylight beyond: the sculpture is 60 cm high. Borromini was aided in his perspective trick by a mathematician.

The Mannerist stucco sculptural decor of the palazzo's front and its courtyard façades feature sculptures crowded into niches and fruit and flower swags, grotesches and vignettes of symbolic devices (impresi) in bas-relief among the small framed windows of a mezzanine, the richest cinquecento façades in Rome.
 
Facade details.

The colossal sculpture of Pompey the Great, erroneously believed to be the very one at whose feet Julius Caesar fell, was discovered under the party wall of two Roman houses in 1552: it was to be decapitated to satisfy the claims of both parties, which appalled Cardinal Capodiferro so, that he interceded on the sculpture's behalf with Pope Julius III, who purchased it and then gave it to the Cardinal.

Cardinal Spada's collection, which includes four galleries of 16th and 17th-century paintings by Andrea del Sarto, Guido Reni, Titian, Jan Brueghel the Elder, Guercino, Rubens, Dürer, Caravaggio, Domenichino, the Carracci, Salvator Rosa, Parmigianino, Francesco Solimena, Michelangelo Cerquozzi, Pietro Testa, Giambattista Gaulli, and Orazio and Artemisia Gentileschi, has the additional interest of being hung in the 17th-century manner, frame-to-frame, with smaller pictures "skied" above larger ones.

Palazzo Spada was purchased by the Italian State in 1927 and today houses the Italian Council of State, which meets in its richly frescoed and stuccoed rooms.