Alessandro Campeggio was born in Bologna on 12 April 1504, the son of Lorenzo Campeggio and Francesca Guastavillani.[1] His father was married and had five children, but after the death of Francesca, he entered the ecclesiastical estate and himself became a cardinal.[1] Educated at home, Alessandro Campeggio studied Italian letters, Latin, Ancient Greek, philosophy, and Christian theology.[1]
He was elected Bishop of Bologna on 19 March 1526.[1] He was constituted administrated administrator of the diocese until he reached the canonical age of 27.[1] Upon reaching the canonical age, he delayed receiving episcopal consecration, receiving an prorogation on 11 December 1529, again on 24 August 1539 and again on 10 April 1540.[1] On 19 July 1541 he was finally granted license to receive Holy Orders.[1] As such, he was ordained as a priest and consecrated as a bishop on 31 July 1541 in the church of San Michele in Bosco in Bologna.[1]
On 15 October 1541 he was nominated to be vice-legate in Avignon.[1] As such, he arrived in Carpentras on 10 November 1542 and remained there until 1544. On 14 August 1544 he was appointed a cleric of the Apostolic Camera.[1] When the Council of Trent was moved from Trent to Bologna, he hosted the conciliar fathers in his own palace from 12 March 1547 until 10 November 1549.[1]