Cosimo III de' Medici (14 August 1642 – 31 October 1723) was Grand Duke of Tuscany from 1670 until his death in 1723, the sixth and penultimate from the House of Medici. He reigned from 1670 to 1723, and was the elder son of Grand Duke Ferdinando II. Cosimo's 53-year-long reign, the longest in Tuscan history, was marked by a series of laws that regulated prostitution and May celebrations. His reign also witnessed Tuscany's deterioration to previously unknown economic lows.
Cosimo III married Marguerite Louise d'Orléans, a cousin of Louis XIV. The marriage was solemnized by proxy in the King's Chapel at the Louvre, on 17 April 1661. It proved to be a very difficult marriage. Marguerite eventually abandoned Tuscany for the Convent of Montmartre. Together, they had three children: Ferdinando in 1663, Anna Maria Luisa, Electress Palatine, in 1667, and Gian Gastone I the last Medicean ruler of Tuscany, in 1671.
In later life, Cosimo III attempted to have his daughter recognised as the universal heiress of Tuscany, after his sons (who did not look like they would produce heirs), but Charles VI, Holy Roman Emperor, would not allow it because Tuscany was an imperial fief, and he felt he alone could alter the Tuscan laws of succession. In 1723, when Cosimo died, he was succeeded by his younger son. All Cosimo III's efforts to salvage the throne for his family foundered, and in 1737, upon the death of Gian Gastone, Tuscany passed to the House of Lorraine.
Cosimo de' Medici was born on 14 August 1642, the eldest surviving son of Vittoria della Rovere of Urbino, and Ferdinando II de' Medici, Grand Duke of Tuscany. Their previous two children had died shortly after birth. Although Grand Duke Ferdinando wanted to give his son the finest scientific education available, the pious Grand Duchess Vittoria opposed that wish, and got her way. Volunnio Bandinelli, a Sienese theologian, was appointed Cosimo's tutor. His character was similar to the Grand Duchess's.
As a youth, Cosimo revelled in sports. His uncle Gian Carlo once wrote to another family member with "news that should surprise you....The young prince [Cosimo] has killed a goose in mid-air." Cosimo, at the age of 11, killed five pigs with five shots. The Luchese ambassador highly praised the young Cosimo. His successor, however, described Cosimo as "melancholy". In his early youth, he was in love with a man named Petrillo, a singer. Their romance was discovered when Cosimo spontaneously hugged and kissed him in front of a tutor. Petrillo fled Florence, never to return. Cosimo's father knew of his homosexual nature and tried to force him to take a wife, as Cosimo presented the best possibility of begetting an heir. In 1687, he had a boyfriend in Venice, Cecchino, nicknamed de' Castris, because he was castrated.
By 1659, Cosimo had ceased smiling in public. He frequently visited places of religious worship and surrounded himself with friars and priests, worrying Grand Duke Ferdinando. Cosimo's only sibling, Francesco Maria de' Medici, the fruit of his parents' brief reconciliation, was born the next year.
Marguerite Louise d'Orléans, a granddaughter of Henry IV of France, was married to Cosimo by proxy on 17 April 1661 at the Louvre Palace. She arrived in Tuscany on 12 June, disembarking at Livorno, and made her formal entry to Florence on 20 June to much pageantry. As a wedding gift, Grand Duke Ferdinando presented her with a pearl the "size of a small pigeon's egg."
The marriage was unhappy from the start. A few nights following the formal entry, Marguerite Louise demanded the Tuscan crown jewels for her own personal use; Cosimo refused. The jewels that she did manage to extract from Cosimo were almost smuggled out of Tuscany by her attendants but for the efforts of Ferdinando's agents.
Marguerite Louise's extravagances perturbed Ferdinando because the Tuscan exchequer was nearly bankrupt; it was so empty that when the Wars of Castro mercenaries were paid for, the state could no longer afford to pay interest on government bonds. Accordingly, the interest rate was lowered by 0.75%. The economy, too, was so decrepit that barter trade became prevalent in rural marketplaces. In August 1663 Marguerite Louise delivered a boy: Ferdinando. Two more children followed: Anna Maria Luisa in 1667 and Gian Gastone in 1671.
Ferdinando beseeched Louis XIV to do something about his daughter-in-law's behaviour; he sent the Comte de Saint-Mesme. Marguerite Louise wanted to return to France, and Saint-Mesme sympathised with this, as did much of the French court, so he left without finding a solution to the heir's domestic disharmony, incensing both Ferdinando and Louis XIV. She humiliated Cosimo at every chance she got: she insisted on employing French cooks, as she feared the Medici would poison her. In September 1664 Marguerite Louise abandoned her apartments in the Pitti Palace. Cosimo moved her into Villa Lapeggi. Here, she was watched by forty soldiers, and six courtiers—appointed by Cosimo—had to follow her everywhere. The next year she reconciled with the grand ducal family, and gave birth to Anna Maria Luisa, future Electress Palatine, in August 1667. The delicate rapprochement that existed between Marguerite Louise and the rest of the family collapsed after Anna Maria Luisa's birth, when Marguerite Louise caught smallpox and decided to blame Cosimo for all her problems.
Grand Duke Ferdinando encouraged Cosimo to go on a European tour to distract him from Marguerite Louise's renewed hostility. On 28 October 1667 he arrived in Tyrol, where he was entertained by his aunt, Anna de' Medici, Archduchess of Further Austria. He took a barge down the Rhine to Amsterdam, where he was well received by the art community, meeting painter Rembrandt van Rijn. From Amsterdam, he travelled to Hamburg, where awaiting him was Queen Christina of Sweden. He reached Florence in May 1668. There he took in the painter and architect Pier Maria Baldi as a chamberlain, who accompanied him through the rest of his travels through Europe. Another great personage that accompanied Cosimo was the Italian philosopher and diplomat Lorenzo Magalotti, who proceeded to document and describe their travels.
The excursion did Cosimo good. His health was better than ever, as was his self-esteem. His wife's unrelenting enmity towards him, however, undid the aforesaid progressions. Grand Duke Ferdinando, once again, feared for his health, so he sent him on a second tour in September 1668.
When he went to Spain, the disabled King Charles II received him in a private interview. By January 1669, he had arrived in Portugal, being welcomed by the Court and Peter II, where he stayed until March, visiting several villages and cities such as Lisbon, Setúbal, Santarém, Coimbra, Rates and Viana. Of the various monuments, convents and churches visited, it was the Monastery of Saint Denis of Odivelas that most aroused the curiosity of the Florentines due to the libertine lifestyle of the nuns living there. In Lisbon, Cosimo also had the opportunity to talk several times with the Jesuit Priest António Vieira and to attend his famous masses. After leaving Caminha by sea they arrived at La Coruña where they took another ship. At some point, the ship met an uncomfortable storm that made them land in Kinsale, Ireland. From there they went to England, where he met Charles II. Samuel Pepys described him as "a very jolly and good comely man." Cosimo was amiably welcomed by the Universities of Oxford and Cambridge, for his father's perceived protection of Galileo Galilei from the Inquisition. He met with scientists such as Robert Hooke, Henry Oldenburg, Isaac Newton and Robert Boyle; Cosimo bought a machine, built by Samuel Morland. In London, he stayed at St. Albans House as a guest of the Earl of St Albans.
On the return, he travelled again through the Dutch Republic; this time he bought a self-portrait which Rembrandt had finished in the meantime. He visited Jan Swammerdam and his collection of insects. Passing Aachen, Cosimo visited Louis XIV and his mother-in-law, Marguerite of Lorraine, in Paris. He arrived back in Florence on 1 November 1669. His travels were described in a detailed journal by his travelling companion Lorenzo, Conte Magalotti (1637–1712).