Stella de’ Tolomei was an Italian noblewoman and the official mistress of Niccolò III d'Este, Marquis of Ferrara. Although never married to Niccolò, she held a prominent position at the Este court and bore him several children, including Leonello d'Este, who later became Marquis of Ferrara, and Borso d'Este, the first Duke of Ferrara. Her relationship with Niccolò granted her significant status and influence during her lifetime.