After 984 Ferrara was a fief of Tedaldo, count of Modena and Canossa, nephew of the emperor Otto I.
It afterwards made itself independent, and in 1101 was taken by siege by the countess Matilda.
At this time it was mainly dominated by several great families, among them the prominent Adelardi (or Aleardi) family.In 1146, Guglielmo II of Adelardi, the last of the House of Adelardi, died, and his property passed, as the dowry of his niece the Marchesella, to Obizzo I of Este.
There was considerable hostility between the newly entered family and the prominent Salinguerra family, but after considerable struggles Azzo VII of Este was nominated perpetual podestà in 1242; in 1259 he took Ezzelino of Verona prisoner in battle.
His grandson, Obizzo II (1264–1293), succeeded him, and he was made perpetual lord of the city by the population in 1264.
He also became seignior of nearby Modena in 1288 and of Reggio in 1289.The House of Este was from henceforth settled in Ferrara.
In 1289 he was also chosen as lord of Modena, one year later he was made lord of Reggio.
Niccolò III (1393–1441) received several popes with great magnificence, especially Eugene IV, who held a council here in 1438.
His son Borso receives the title of duke for the imperial fiefs of Modena and Reggio from Emperor Frederick III in 1452 (in which year Girolamo Savonarola is born here).
