Marie Bonaparte was the daughter of Prince Roland Bonaparte (1858-1924), a distinguished scientist, and of Marie-Flix Blanc (1859-1882), one of the two daughters of Franois Blanc (d 1877), whose huge fortune came from the Socit des Bains de Mer of Monte Carlo. At the time, Marie-Flix's marriage was considered a great social triumph, as indeed was her daughter's union with Prince George of Greece and Denmark, through whom Marie became related to most of the crowned heads of Europe. In her memoirs, "A La Memoire des Disparus" (1958), Marie acknowledged that it was her mother, a talented musician, who bequeathed to her a love of music and poetry, as well as the Blanc wealth.

Marie was known for her love of jewels and beautiful clothing. In 1907, prior to her marriage, her trousseau and jewellery, which included exquisite objects by Cartier, were put on public display (much to her own embarrassment) and photographs were published by "The Illustrated London News". She was particularly fond of her rings, and later in life, when obliged to wear gloves on court occasions, hers were always made of transparent nylon. When she was asked why, she would reply: "On voit les bagues mieux, je les prfre."