Caterina Sforza, Countess of Forli and Imola (1463-1509)
She was daughter of Galeazzo Maria Sforza by Lucrezia Landiani, and was later legitimized. At the age 15 she gave birth to the first of 7 children in nine years. Her first husband, Girolamo Riario, was murdered in 1488 by the Orsi family and she was taken captive with the children - but escaped. Caterina got help from Milano and Bologna.
From here on, Caterina became noted as a brutal tyrant, initially as regent for her son, Ottaviano. In Forlì it was Caterina who issued justice, especially after the revolt in 1487 in which her husban failed to do anything. Caterina was also involved in a plot and tried to poison Pope Alexander VI. Perhaps it is for all these reasons that Renaissance men referred to her as "the Virago", or woman warrier.
Married her second husband, Giacomo Peo, around 1490 and had a son with him, before he was murdered 1495. Her third husband was Giovanni di Pierfrancesco de Medici, who died of natural causes after one year of marriage. She continued to rule her small lands until they were attacked by Cesare Borgia in 1499. She was then imprisoned in Belvedere Palace at the Vatican for four months. After a failed escape attempt, Caterina was imprisoned in Castel Sant' Angelo for one year. She was released after having given up her lordship, and died eight years later in Firenze.
Machiavelli was sent as an envoy to Caterina in 1499.