Ferdinando II de' Medici (14 July 1610 – 23 May 1670) was grand duke of Tuscany from 1621 to 1670. He was the eldest child of Cosimo II de' Medici and Maria Maddalena of Austria. His 49-year rule was punctuated by the beginning of Tuscany's long economic decline. He married Vittoria della Rovere, with whom he had two children: Cosimo III de' Medici, his eventual successor, and Francesco Maria de' Medici, Duke of Rovere and Montefeltro, a cardinal.

Ferdinando was the eldest son of Cosimo II de' Medici, Grand Duke of Tuscany and Maria Maddalena of Austria. Cosimo II died when Ferdinando was 10; because he had not yet reached maturity, his mother and paternal grandmother, Christina of Lorraine, acted as joint regents. In his seventeenth year, Ferdinando embarked on a tour of Europe. One year later, his regency ended and his personal rule began. Dowager Grand Duchess Christina was the power behind the throne until her death in 1636.

Ferdinand, like Christina before him, was a patron, ally, and friend of Galileo. Galileo dedicated his Dialogue Concerning the Two Chief World Systems to him. This work led to Galileo's second set of hearings before the Inquisition. Ferdinand attempted to keep Rome's concerns from leading to a full-fledged hearing and kept Galileo in Florence until December 1635, when the Roman Inquisitors finally threatened to bring Galileo to Rome in chains if he would not come voluntarily. Ferdinand's influence likely contributed to the lightness of Galileo's penalty after the court's conviction of the astronomer for "vehement suspicion of heresy;" and the devoutly Catholic Ferdinand welcomed Galileo back to Florence after the trial was over.

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