Leonello d'Este (also spelled Lionello; 21 September 1407 – 1 October 1450) was marquis of Ferrara and Duke of Modena and Reggio Emilia from 1441 to 1450.
Leonello was one of the three illegitimate sons of Niccolò d'Este III and Stella de' Tolomei. He received a military education under the condottiero Braccio da Montone, and was taught in letters by the humanist Guarino Veronese. In 1425, after the execution of his elder brother Ugo Aldobrandino, he remained the sole heir of Niccolò.
In 1435 he married to Margherita Gonzaga and was renowned as legitimate son by Pope Martin V. Margherita, who died in 1439, gave birth to a child, Niccolò in 1438 (died in 1476).
In 1441 he succeeded his father to his possession in northern Italy. In 1444 Leonello married to Mary of Aragon, illegitimate daughter of King Alfonso V of Naples.
Leonello was responsible of the construction of the first hospital of Ferrara. A skilled politician, he however distinguished chiefly as a man of culture. Leon Battista Alberti wrote his De Re Aedificatoria under Leonello's commission, and at the Ferrarese court worked artists such as Pisanello, Iacopo Bellini, Giovanni da Oriolo, Andrea Mantegna, Piero della Francesca and the Netherlandish Rogier van der Weyden. During his rule the University of Ferrara gained a European prestige.
Leonello died in 1450, at age 43. He was succeeded by his father's illegitimate son, Borso d'Este.
| Preceded by Niccolò III |
Marquess of Ferrara Modena and Reggio 1441–1450 |
Succeeded by Borso |