Lovisa Sofia "Louise Sophie" von Fersen, née Piper (1777-1849), was a Swedish countess and courtier.
Louise von Fersen was the daughter of court chamberlain Sten Abraham Piper and Catharina Ehrensvärd, who had been hovfröken (maid of honour) prior to her marriage. She served as maid of honour to princess Sophia Albertina of Sweden in 1794-1797, and married the courtier count Fabian Reinhold von Fersen in 1797. By marriage, she became the sister-in-law to the famous Axel von Fersen the Younger as well as Sophie Piper, who was married to her brother Carl Piper.
She served as hovmästarinna (deputy mistress of the robes) in 1804-05 and överhovmästarinna (Mistress of the Robes) in 1805-09 to queen Frederica, and Mistress of the Robes to queen Charlotte in 1809-1810.
H. G. Trolle Wachtmeister said of her that she "was the most beautiful Juno-like figure you could see" and "undoubtedly the most accomplished woman in high society".