Alfonso d'Este, Marquis of Montecchio (10 March 1527 – 1 November 1587) was an Italian nobleman from the House of Este.

Born at Ferrara, he was the illegitimate son of Alfonso I d'Este, Duke of Ferrara by his lover Laura Dianti. In 1523 his father gave him Montecchio Emilia and turned it into a feudal inheritance for cadet members of his family^[1] – in 1569 it was promoted to a marquessate by Maximilian II, Holy Roman Emperor.^[1]

Alfonso was legitimated in 1532 by cardinal Innocenzo Cybo and in 1533 by his father Alfonso I.^[2] His first marriage followed on 3 January 1549, to Giulia della Rovere, daughter of Francesco Maria I della Rovere, Duke of Urbino and Eleonora Gonzaga. In 1584 he married Violante Signa (1546–1609), with whom he had one daughter and a son.^[3] He died at Ferrara in 1587.

Alfonso had by Giulia della Rovere (1527-1563) the following children:^[4]

• Alfonso d'Este (1560–1578), married Marfisa d'Este;
• Cesare d'Este (1562–1628), married Virginia de' Medici. The legitimacy of the succession was recognized by the Emperor Rudolph II but not by Pope Clement VIII: thus, as Ferrara was nominally a Papal fief, the city was returned to the Papal States, despite the attempts of the young duke, who sought help from the Major Powers to no avail. The Este family thus lost the duchy of Ferrara.
• Eleonora d'Este (1561–1637), married Carlo Gesualdo di Venosa.

He also had by Violante Signa (1546-1609) the following children:^[5]

• Ippolita d'Este (1565–1602), married Federico Pico, Duke of Mirandola.
• Alessandro d'Este (1568–1624), Cardinal.