Palazzo dei Diamanti is a Renaissance palace located on Corso Ercole I d'Este 21 in Ferrara, region of Emilia Romagna, Italy.

To accommodate the growth of Ferrara, in 1492 the Duke Ercole I d'Este demolished the medieval walls of the city on the north, and had the court architect, Biagio Rossetti, design an urban expansion known as the Addizione Erculea.

Used as a residential home by the Este family and, starting in 1641, by the Villa marquis, in 1832 the palace was acquired by the municipality of Ferrara to house the National Gallery of Art and the Civic University.

The most striking feature is the bugnato of the exterior walls: it consists of some 8,500 white (with pink veins) marble blocks carved to represent diamonds, hence its name.

Among the other artists in the collection are Amerigo Aspertini, Giuseppe Avanzi, Baldassarre d'Este, Jacopo Bambini, Bastarolo (Giuseppe Mazzuoli), Giovanni Bellini, Jacopo Bellini, il Ortolano, Carlo Bononi (1569–1632), Vittore Carpaccio, Girolamo da Carpi (1500–1556), Agostino Carracci, Ludovico Carracci, Coltellini (1480–1535/42), Francesco del Cossa (1435/1436–1478), Lorenzo Costa (c. 1460–1535), Giulio Cromer, Girolamo Domenichini, Battista Dossi (c. 1490–1548), Francesco Francia (1450–1517), Gaetano Gandolfi, Ubaldo Gandolfi, Maestro degli Occhi Spalancati, Maineri, Giovanni da Modena (active 1398), Ludovico Mazzolino (c. 1480), Panetti, Giacomo Parolini, Nicolò Pisano (Nicolò dell'Abrugia), Nicolò Roselli (1500–c.