Costanza Sforza, duchess of Sora

Costanza Sforza of Santa Fiora (1550 – 22 January 1617) was an Italian noblewoman. By birth she was member of the powerful House of Sforza and by marriage member of the House of Boncompagni.

Early life Costanza was daughter of Sforza Sforza, 1st Marquess of Castell'Arquato, 11th Count of Santa Fiora (1520 – Castell'Arquato, 21 October 1575), and his first wife Luigia Pallavicino (died in 1552), maternal granddaughter of Jacopo Salviati and wife Lucrezia de' Medici. She was a half-sister of Cardinal Francesco Sforza and paternal granddaughter of Costanza Farnese (daughter of Alessandro Farnese, later Pope Paul III). She married Don Giacomo Boncompagni, 1st Marquess of Vignola, and 1st Duke of Sora, Aquino, Arce and Arpino, on 5 February 1576, and had fourteen children.

Lavinia Fontana, a prominent Bolognese artist, painted her portrait in 1594. A year later, Constanza served as the namesake and godmother of Fontana's daughter.