Editing Pope Gregory XIII (section)

===Career before papacy===

At the age of 36 he was summoned to Rome by [[Pope Paul III]] (1534–1549), under whom he held successive appointments as first judge of the capital, [[abbreviator]], and vice-chancellor of the [[Campagna e Marittima]]. 
[[Pope Paul IV]] (1555–1559) attached him as ''[[datarius]]'' to the suite of Cardinal [[Carlo Carafa]]. [[Pope Pius IV]] (1559–1565) made him [[Cardinal-Priest]] of [[San Sisto Vecchio]] and sent him to the [[Council of Trent]].

In the year 1552, Ugo Boncompagni confirmed the paternity of his son Giacomo (or Jacopo). As stated in the online Archivio Digitale Boncompagni Ludovisi: "One of the most valuable items to emerge from the new archival finds from the [[Villa Aurora (Rome)|Villa Aurora]] is an autograph declaration in Latin and Italian dated 22 December 1552 by Ugo Boncompagni (1502–1585, from 1572 Pope Gregory XIII). Here Ugo confirms his paternity of [[Giacomo Boncompagni|Giacomo (or Jacopo) Boncompagni]] (1548–1612) by Maddalena de' Fucchinis, a servant in the employ of his sister-in-law Laura Ferro. The future Pope explains in detail the circumstances of the boy's conception, which took place in 1547 in [[Bologna]] after the Council of Trent had moved to that city; his motive was to assure his inheritance rights following the death (in 1546) of his father Cristoforo Boncompagni."<ref>[https://villaludovisi.org/2012/12/02/1552-ugo-boncompagni-gregory-xiii-confirms-his-paternity-of-giacomo-boncompagni-born-1548/#more-37 New from 1552: Ugo Boncompagni (=Pope Gregory XIII) confirms his paternity of son Giacomo]</ref>

He also served as a legate to [[Philip II of Spain]] (1556–1598), being sent by the Pope to investigate the [[Roman Catholic Archdiocese of Toledo|Archbishop of Toledo]] [[Bartolomé Carranza]]. He formed a lasting and close relationship with the Spanish king, which aided his foreign policy aims as Pope.<ref>{{Cite web |date=2017-01-27 |title=Pope Gregory XIII - PopeHistory.com |url=https://popehistory.com/popes/pope-gregory-xiii/ |access-date=2025-01-27 |website=popehistory.com |language=en-US}}</ref>