Duke of Valentinois Pierre

Monegasque prince, who married into the House of Grimaldi, and was father of Rainier III, Prince of Monaco. He was a promoter of art, music, and literature in Monaco and served as the head of the country's delegation to the United Nations Educational, Scientific, and Cultural Organization (UNESCO) and to the International Olympic Committee.

He was the fourth son and youngest child of Count Maxence Melchior Edouard Marie Louis de Polignac (1857–1936) and his Mexican-born wife, Susana Mariana Estefanía Francisca de Paula del Corazón de Jesús de la Torre y Mier (1858–1913), whom he wed in Paris in 1881.

He married civilly on 19 March and religiously on 20 March 1920, in Monaco, Princess Charlotte of Monaco, the illegitimate but adopted daughter of Louis II of Monaco by Marie Juliette Louvet.

He and his wife had two children, Princess Antoinette, Baroness of Massy (1920–2011) and Rainier III, Prince of Monaco (1923–2005).

His unhappy arranged marriage was complicated by his homosexuality and Princess Charlotte's affairs. In the mid-1920s, the couple unofficially separated, with Pierre living in his Paris apartment and on an estate near the city, when not in Monaco. Prince Pierre and Princess Charlotte were judicially separated on 20 March 1930 at Paris, and in a case titled "Princesse héréditaire Grimaldi de Monaco c. Prince Pierre Grimaldi de Polignac" were divorced by ordinance of Prince Louis II on 18 February 1933.

Prince Pierre died of cancer on 10 November 1964 at the American Hospital in Neuilly-sur-Seine, Paris, France. He was 69.