Frederica Louisa of Hesse-Darmstadt (German: Friederike Luise; 16 October 1751 – 25 February 1805) was Queen of Prussia and Electress of Brandenburg as the second wife of King Frederick William II.

Frederica Louisa was selected to marry Frederick William immediately after his divorce from Elisabeth Christine of Brunswick-Lüneburg, after Margravine Philippine of Brandenburg-Schwedt and Sophia Albertina of Sweden had been suggested.

She is of the middle size, her countenance agreeable, though not handsome, her manners easy and engaging, her character estimable and formed to excite universal respect.

[1] The marriage was not happy, and Frederick William had numerous lovers, most notably Wilhelmine von Lichtenau, with whom he had a relationship from the same year he married Frederica Louisa until his death.

[1] She mainly resided in Potsdam, "in the most monotonous and wearisome seclusion, neglected by her husband, slighted by the king, and seldom allowed even the diversion of a visit to Berlin".

Her brother-in-law Duke Karl August of Saxe-Weimar was appointed ambassador in the negotiations between the king and queen, and Frederica Louisa was eventually obliged to agree.

[1] During this affair, the German theatre gave the play "Inez de Castro" several nights in a row, it attracted great attention that the queen always retired during the performance of the fourth act, where the prince makes vows of passionate love to the maid of honour, and it was speculated whether this was a demonstration or not.

[1] When Wilhelmine, Gräfin von Lichtenau was finally given the title of countess, Frederica Louisa was obliged to receive her officially at court and present her with her portrait set in brilliants upon the advice of her own favorites, her Oberhofmeister Wittgenstein and her gentlewoman of the chamber.

[1] When the king fell ill in 1796, he was tended by von Lichtenau, who after his temporary recovery in the spring of 1797 hosted the opera La Morte di Cleopatra by Nasolini in her garded, to which the queen was commanded to attend, an occasion which attracted a lot of attention and was described by Dampmartin: On his deathbed, the king was attended by Wilhelmine Lichtenau in Potsdam, while the queen stayed in Berlin and visited him once a week.

[1] Frederica Louisa had a good relationship with her son Frederick William III of Prussia, who had resented his mother being put aside by his father and made a point of placing her in a high position of honour and respect, but there is almost no information of her during her years as a widow.

The Swedish Princess Hedwig Elizabeth Charlotte described her at the time of her visit in 1798: The Queen Dowager had invited us at déjeuner, and we left for Montbijou, a very simple manor slightly outside of Berlin, where she resides all year.