Girolamo Aleandro (also Hieronymus or Jerome Aleander) (13 February 1480 – 1 February 1542) was an Italian cardinal, and the first cardinal appointed in pectore.
Aleandro was born on 13 February 1480 in Motta di Livenza, in the province of Treviso, part of the Republic of Venice. He studied in Venice, where he became acquainted with Erasmus and Aldus Manutius, and at an early age was reputed one of the most learned men of the time. In 1508 he went to Paris on the invitation of Louis XII as professor of belles lettres, and held for a time the position of Rector of the University of Paris. He was an early teacher of Greek at the University and edited texts by Isocrates and Plutarch printed by Gilles de Gourmont in 1509/1510. Entering the service of Eberhard, prince-bishop of Liège, he was sent by that prelate on a mission to Rome, where Pope Leo X retained him, giving him (1519) the office of librarian of the Vatican. In the following year he went to Germany to be present as papal nuncio at the coronation of Emperor Charles V, and was also present at the Diet of Worms, where he headed the opposition to Martin Luther, advocating the most extreme measures to repress the doctrines of the reformer. His conduct evoked the fiercest denunciations of Luther, but it also displeased more moderate men, especially Erasmus. The edict against the reformer, which was finally adopted by the emperor and the diet, was drawn up and proposed by Aleandro. After the close of the Diet, the papal nuncio went to the Netherlands, where he instigated the executions of two monks of Antwerp due to their embrace of the Reformation, resulting in their being burnt in Brussels.