Leonello d'Este (also spelled Lionello; 21 September 1407 – 1 October 1450) was Marquess of Ferrara, Modena, and Reggio Emilia from 1441 to 1450. Despite the presence of legitimate children, Leonello was favoured by his father as his successor. In addition, his virtuous qualities, high level of education, and popularity among the common people as well as his formal papal recognition ultimately made him the most suitable heir.
Leonello had little influence over the Italian political landscape and aristocracy in Ferrara. Contrary to other prior d’Este family leaders, such as Azzo VII, Niccolò III, and Isabella d’Este, who had a drive for power and control, Leonello is recognized principally for his sponsorship of the arts, literature, and culture. In 1441–1450, his learned courts and developing knowledge assisted him in transforming the city of Ferrara. Under the guidance of Guarino Veronese, his humanist teacher, and with the approval of the commune, Leonello began the reformation, particularly, the University of Ferrara.
Leonello not only elevated the humanistic cultural movements during his rule, but it also influenced the political and artistic advancements of his successors. Leonello d’Este served as the precursor of the achievements in the history of the House of Este.
Leonello was one of 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 tutored by Guarino Veronese, later appointed professor at the University of Ferrara, who also instructed him on the traits of a desirable ruler and how to govern. In 1425, after the execution of his elder brother Ugo Aldobrandino, he was the sole heir of Niccolò. In 1435, he married Margherita Gonzaga on 6 February and was recognized as legitimate son by Pope Martin V. Margherita, who died in 1439, gave birth to a child, Niccolò, in 1438, who is also known as Niccolò di Leonello to avoid confusion with his grandfather Niccolò d'Este III. Niccolò the son died in 1476. In late December 1441, Leonello succeeded to his father's possessions after his death in northern Italy.
Coming from a strong academic background, Leonello brought significant unprecedented economic, political, and cultural changes to Ferrara right after he took over from Niccolò III. In May 1444, Leonello married Mary of Aragon who was at the age of 19, an illegitimate daughter of King Alfonso V of Naples. The marriage was a political one. To ensure the political stability within Ferrara, Leonello remained neutral in the political affairs between Milan and Venice. However, Leonello had a much broader picture for Ferrara, expanding its authority and power in its area. After the death of Margherita Gonzaga, Leonello saw the opportunity of forming alliances with neighboring regions through kinship to strengthen its power. The victory of Alfonso V in Naples, the father of Mary of Aragon, acted as a catalyst for such a diplomatic marriage for Leonello and an opportunity for Ferrara.
Not much progress was made during the rule of Niccolò III as he focused more on political matters and economic prosperity within Ferrara. Leonello was a skilled politician and was responsible for the construction of the first hospital of Ferrara. But he distinguished himself chiefly as a man of culture. Leon Battista Alberti wrote his De Re Aedificatoria at Leonello's commission, and at the Ferrarese court there worked artists such as Pisanello, Iacopo Bellini, Giovanni da Oriolo, Andrea Mantegna, Piero della Francesca and the Netherlandish Rogier van der Weyden. His personal breviary was sold in a fragmented state in 1958 by Baron Llangattock at Christie's. It has since then been known as the Llangattock breviary. It was created under the artistic direction of Giorgio d´Alemagna and painters like Matteo De Pasti and Jacopo Magnanimo contributed to it. Leaves from it are in the collections of museums such as the Louvre in Paris, the Danish National Library, and several private collections.
During his rule, the University of Ferrara gained a European prestige.
Leonello died in 1450, aged 43. He was succeeded by Borso d'Este, his father's illegitimate son.
Leonello d’Este's father, Niccoló d’Este III, was also an illegitimate son himself. At the age of nine, Niccoló became legitimated as the successor of Leonello's grandfather, Alberto. However, Leonello's circumstances for securing his rights to succession differed from his father's, primarily because Niccoló was Alberto's only son while Leonello was in a competition with his younger legitimate brothers.
In the presence of his legitimate sons from his later marriage, Niccoló needed to prove that Leonello was qualified to be chosen as his successor. Niccoló defended Leonello's rights to succession on three grounds: Leonello's personal attributes, popularity among his subjects, and official papal recognition. Leonello was often praised for exhibiting strong leadership skills and virtuous characteristics, which would make him a worthy heir and future ruler of Ferrara. In addition, Leonello was taught under esteemed humanist teachers such as Guarino da Verona. His father noted that this high level of education further distinguished Leonello from his siblings. Leonello was also popular among the people and his father recognized the wide support that Leonello would receive from his subjects, who approved of Leonello being chosen as Niccoló's successor. Furthermore, the papacy officially recognized Leonello as a legitimate heir. Thus, by 1434, Leonello was given a great deal of authority to co-rule with his father.
Leonello's succession and subsequent marriage would also serve an important role in relations with neighbouring city-states. Previously, the House of Este owed a great debt to Gianfrancesco Gonzaga, the ruler of Mantua. Instead of having this debt paid monetarily, Gonzaga agreed to have his daughter Margarita marry Leonello, in exchange for Niccoló promising his daughter's line of descendants the position of lords in Ferrara. Hence, the two rulers sought to use the marriage of their children to both their advantages, by resolving the issue of debt and also improving their relationship with the other city-state. This was also advantageous for Leonello, as he was guaranteed political support from another ruler through his marriage.
Meanwhile, Leonello's younger legitimate brothers were also vying for the same position. Because of the potential political conflict that could arise between these siblings, Leonello's father was very cautious of officially appointing Leonello as his successor. Although Leonello was able to co-rule with his father since 1434, Niccoló waited until his last will, which was written just before his death, to formally recognize Leonello as his heir. Niccoló's final will also protected the claims of his legitimate sons Ercole and Sigismondo and ensured that they were each given 10,000 ducats. Following his father's death in 1441, Leonello finally became recognized as the formal heir and the new Marquis of Ferrara.
The circumstances of Leonello's succession as an illegitimate son fit into the historical context of successions in the House of Este. The history of heirs in the House of Este was distinct from those of other Italian city-states because of the frequency of illegitimate sons being chosen as the future heirs. This also reflects the gender attitudes regarding the political successions in the House of Este during this time period. A greater preference was given for illegitimate sons to become successors, instead of legitimate daughters. Leonello himself was also succeeded by a man who had an illegitimate birth status. His brother, Borso, who was born from the same mother of Leonello, was later chosen to be Leonello's successor.
The University of Ferrara dates back to 1391. It was not until 1442—one year into the reign of Leonello d’Este—that it became a fully operational university with an adequate number of professors to instruct the major subjects of canon law (church law), logic, philosophy and medicine. Hence, while the traditional date for the beginning of the university is 1391, 1442 is now considered its true founding date, because that is when it grew in size and overall awareness within Ferrara and the surrounding towns. When the university was granted the charter to be allowed to grant degrees on 4 March 1391 in civil and canon law, arts, medicine and theology, the university had only two professors of law, and no evidence has been found of university-level arts and theology instruction. The university was closed down in 1394, less than three years after its opening. Due to wartime expenses, teaching ceased in 1404; in 1418 Niccolò III – the father of Leonello, who ruled from 1393 to 1441 – tried but was unsuccessful in reopening the university.