Alfonso d'Este (21 July 1476 – 31 October 1534) was Duke of Ferrara during the time of the War of the League of Cambrai.
He was the son of Ercole I d'Este and Eleanor of Naples and became duke on Ercole's death in June 1505. In the first year of his rule he uncovered a plot by his brother Ferrante and half-brother Giulio d'Este, directed against him and his other brother Ippolito. In September 1506 a trial for lèse majesté and high treason was held and, as expected, the death sentence was passed, but just as Ferrante and Giulio were about to mount the gallows they were informed that the duke had commuted their sentence to life imprisonment. They were led away to two cells in the Torre dei Leoni. Ferrante died in his cell after 34 years of imprisonment, while Giulio held on until he was pardoned in 1559, after 53 years of imprisonment. After his release, Giulio was ridiculed in the streets of Ferrara for his outdated clothes and died in 1561.
The House of Este ([ˈɛste] Italian: Casa d'Este, originally House of Welf-Este) is a European princely dynasty. It is one of the most ancient noble dynasties in Europe.
The elder branch of the House of Este included the dukes of Brunswick and Lüneburg (1208–1918) and produced Britain's Hanoverian monarchs and one Emperor of Russia (Ivan VI).
The younger branch of the House of Este included rulers of Ferrara (1240–1597), and Modena and Reggio (1288–1796).
Edward Gibbon said the family originated from the Roman Attii family, which migrated from Rome to Este to defend Italy against the Ostrogoths. However, there is little evidence to support this hypothesis. The names of the early members of the family indicate that a Frankish origin is much more likely. The first known member of the house was Margrave Adalbert of Mainz, known only as father of Oberto I, Count palatine of Italy, who died around 975. Oberto's grandson, Albert Azzo II, Margrave of Milan (996–1097) built a castle at Este, near Padua, and named himself after it. He had three sons from two marriages, two of whom became the ancestors of the two branches of the family: