Princess Polyxena of Hesse-Rheinfels-Rotenburg (Polyxena Christina Johanna; 21 September 1706 – 13 January 1735) was the second wife of Charles Emmanuel, Prince of Piedmont whom she married in 1724. The mother of the future Victor Amadeus III, she was Queen of Sardinia from 1730 until her death in 1735.^[3]

Polyxena was born as the eldest daughter of Ernst Leopold, Landgrave of Hesse-Rheinfels-Rotenburg and Princess Eleonore of Löwenstein-Wertheim-Rochefort, daughter of Maximilian Karl Albert, Prince of Löwenstein-Wertheim-Rochefort.

King Victor Amadeus II of Sardinia approached her family and proposed a union between Polyxena and Victor Amadeus II's son and heir, Charles Emmanuel, Prince of Piedmont. A previous match orchestrated by Agostino Steffani with a daughter of Rinaldo d'Este, Duke of Modena, had come to nothing.^[4] His first wife, Countess Palatine Anne Christine of Sulzbach, died on 12 March 1723, less than a year after her marriage and barely a week after giving birth to a son, Victor Amadeus, Duke of Aosta (7 March 1723 – 1 August 1725).^[5]

Although only two years younger, Polyxena was a niece of Charles Emanuel's first wife,^[5] and belonged to the Hesse-Rotenburg line, which was the only Roman Catholic branch (since 1652) of the reigning House of Hesse.^[6] She had been nominally a canoness of Thorn Abbey since 1720.^[7]

The engagement was announced on 2 July 1724,^[8] and she wed Charles Emmanuel by proxy on 23 July in Rotenburg. The marriage was celebrated in person at Thonon in Chablais on 20 August 1724.^[9]

Her stepson Victor Amadeus, heir after his father and grandfather to the Sardinian crown, died at the age of two, a year after Polyxena's marriage and before she had a child of her own. Nonetheless, she is said to have had a close relationship with her mother-in-law, Anne Marie d'Orléans, and the two frequented the Villa della Regina outside the capital, where the latter died in 1728.

When King Victor Amadeus announced his decision to return to the throne after having abdicated in 1730, Polyxena used her influence over her husband^[10] to have his father imprisoned at the Castle of Moncalieri, where he was joined for a while by his morganatic wife, Anna Canalis di Cumiana, Polyxena's former lady of the bedchamber.^[11]

In an 1869 history of the House of Savoy, Francesco Predari wrote that despite the fact Polyxena was praised for goodness of character and beautiful virtues, her father-in-law advised her to take care to maintain separate quarters from her husband for prudence's sake.^[8] In 1732 she founded a home for young mothers in Turin,^[8] redecorated the Villa della Regina, Stupinigi's hunting lodge, and the Church of Saint Joseph in Turin. She carried out various improvements with Filippo Juvarra and popularised chinoiserie. She was also a patron of Giovanni Battista Crosato, a baroque painter.^[12]

Having been ill since June 1734, she died at the Royal Palace of Turin, and has been buried in the Royal Basilica of Superga since 1786. Two years after her death, her widower married Princess Elisabeth Therese of Lorraine,^[13] sister of the future Francis I, Holy Roman Emperor.

The senior branch of the House of Savoy ended with her grandson Charles Felix of Sardinia. The Villa Polissena in Rome is named in her honour.^[14]

• Victor Amadeus III of Sardinia (26 June 1726 – 16 October 1796), had issue.
• Princess Eleonora of Savoy (28 February 1728 – 14 August 1781), unwed.
• Princess Luisa (25 March 1729 – 22 June 1767), unwed.
• Princess Maria Felicita (19 March 1730 – 13 May 1801), unwed.
• Prince Emanuele Filiberto of Savoy, Duke of Aosta (17 May 1731 – 23 April 1735).
• Prince Carlo of Savoy, Duke of Chablais (23 July 1733 – 28 December 1733).^[15]