After the peace ending the Napoleonic Wars reshaped Europe, ushering in the modern era, the Electorate of Hanover (duchy of Brunswick and Lüneburg, held in personal union by the king of Great Britain, George III) was dissolved by treaty.

Ferrara became a significant center of culture under Niccolò d'Este III (1384–1441), who received several popes with great magnificence, especially Eugene IV.

His successors were his illegitimate sons Leonello (1407–1450) and Borso (1413–1471), who was elevated to Duke of Modena and Reggio by Emperor Frederick III in 1452, receiving these duchies as imperial fiefs.

In 1471, he received the duchy of Ferrara as papal fief from Pope Paul II, for which occasion splendid frescoes were executed at Palazzo Schifanoia.

Alfonso II raised the glory of Ferrara to its highest point, continuing the patron of Torquato Tasso and Giovanni Battista Guarini and in general favoring the arts and sciences, as the princes of his house had always done.

The legitimate line ended in 1597 with him; as his heir, Emperor Rudolph II recognized his first cousin Cesare d'Este (1533–1628), member of a cadet branch born out of wedlock, who continued to rule in the imperial duchies and carried on the family name.

Ferrara, on the other hand, was annexed by force of arms in 1598 by Pope Clement VIII on grounds of the heir's illegitimacy and incorporated into the Papal States.

However, the Salic law excluded her, as a woman, from the succession to her father, while she was entitled to succeed her mother since the Salic law was derogated in the Duchy of Massa and Carrara by virtue of a 1529 decree of the Emperor Charles V. When it became obvious that the princely couple would not produce a large offspring, the reigning Duke, Francesco III, set out to prevent Modena from suffering the same fate as Ferrara almost two centuries earlier.

Thus, in 1753, two simultaneous treaties (one public and one secret) were concluded between the House of Este and the House of Austria, by which the Archduke Leopold, Empress Maria Theresa's ninth-born child and third son, and Maria Beatrice were engaged, and the former was designated by Francesco III as heir for the imperial investiture as Duke of Modena and Reggio in the event of extinction of the Este male line.

In January 1771 the Perpetual Diet of Regensburg ratified Ferdinand's future investiture and, in October, Maria Beatrice and he finally got married in Milan, thus giving rise to the new House of Austria-Este.

Ercole was compensated with the small principality of Breisgau in southwestern Germany, and when he died in 1803, it passed to his son-in-law, who in 1806 lost it to the enlarged and elevated Grand Duchy of Baden during the Napoleonic reorganization of the western territories of the defunct Holy Roman Empire.