Costanza Farnese (19 December 1500 – 23 May 1545) was a daughter of Alessandro Farnese^[1] and Silvia Ruffini.^[2] Born before her father became Pope Paul III, her siblings were Pier Luigi, Paul, Ranuccio and Lucrezia.

She married Bosio II Sforza,^[1] count of Santa Fiora e Cotignola, they had:

• Guido Ascanio^[1]
• Alessandro Sforza^[1]
• Sforza Sforza,^[1] whose children were:
  • Francesco Sforza^[1]
  • Alessandro, 7th count of Santa Fiora, duke of Seni and prince of Valmontone, father of cardinal Federico Sforza.
  • Costanza Sforza^[1]
• Mario (1530–1591), count of S. Fiora, married Fulvia Conti^[1]
• Faustina Sforza, married Muzio Sforza of Caravaggio^[1]
• Francesca Sforza, married Girolamo Orsini^[1]
• Camilla, married Besso Ferrero of Masserano^[1]

• McIver, Katherine A. (2016). "An Invisible Enterprise: Women and Domestic Architecture in Early Modern Italy". In McIver, Katherine A. (ed.). Wives, Widows, Mistresses, and Nuns in Early Modern Italy: Making the. Routledge. pp. 159–180.
• Williams, George L. (1998). Papal Genealogy: The Families and Descendants of the Popes. McFarland & Company, Inc.