Aglaé Louise Françoise Gabrielle de Polignac (7 May 1768 – 30 March 1803) was an 18th-century French noblewoman.
She was born at the Château de Versailles in Paris, France, the eldest child and only daughter of Yolande Martine Gabrielle de Polastron and Jules François Armand de Polignac. Her maternal grandparents were Jeanne Charlotte Hérault and Jean François Gabriel, Comte de Polastron. Her paternal grandparents were Diane Marie Adelaide Zephirine Mazzarini-Mancini (3 February 1726 - 27 June 1755) and Marquis Louis Heracle Melchior of Polignac (31 January 1717 - 1792). Her grandmother Jeanne was the daughter of Marguerite Durey de Vieuxcourt (1700–1729) and René Hérault, Seigneur de Fontaine-l'Abbé et de Vaucresson (23 April 1691 - 2 August 1740).
Aglaé's parents were married on 7 July 1767. In the summer of 1775, her mother, Yolande Martine Gabrielle was invited by her sister-in-law to the French Court, she came with her husband and were presented at a formal reception to Queen Marie Antoinette and King Louis XVI.
Aglaé had three siblings, three brothers: Armand Jules Marie Héracle de Polignac, Duc de Polignac (11 January 1771 - 1 March 1847), Jules Auguste Armand Marie de Polignac, Prince de Polignac (14 May 1780 - 30 March 1847) and Camille Henri Melchior, Comte de Polignac (27 December 1781 - 2 February 1855).
At the Château de Versailles, on 11 July 11 1780, at the age of twelve, Aglaé married the Duc de Gramont et Guiche. She then became the Duchess of Guiche and was nicknamed 'Guichette' by her family.
In 1794, according to "The Memoirs of Madame Vigée Lebrun" by Marie-Élisabeth-Louise Vigée-Le Brun, she painted the Duchesse de Guiche wearing a blue turban, in a half-length portrait. She wrote, "...I encountered the Duchesse de Guiche, whose lovely face had not changed in the least."
On 30 March 1803, Aglaé de Polignac died in an accidental house fire at her home in Edinburgh, Scotland.