Princess Marie Bonaparte (2 July 1882 – 21 September 1962), known as Princess George of Greece and Denmark upon her marriage, was a French author and psychoanalyst, closely linked with Sigmund Freud. Her wealth contributed to the popularity of psychoanalysis and enabled Freud's escape from Nazi Germany.

Marie Bonaparte was a great-grandniece of Emperor Napoleon I of France. She was the only child of Roland Napoléon Bonaparte, 6th Prince of Canino and Musignano (1858–1924) and Marie-Félix Blanc (1859–1882). Her paternal grandfather was Prince Pierre Napoleon Bonaparte, son of Lucien Bonaparte, 1st Prince of Canino and Musignano, Napoleon's rebellious younger brother. For this reason, despite her title, Marie was not a member of the dynastic branch of the Bonapartes who claimed the French imperial throne from exile. Her maternal grandfather was François Blanc, the principal real estate developer of Monte Carlo. It was from this side of her family that Marie inherited her great fortune.

She was born at Saint-Cloud, a town in Hauts-de-Seine, Île-de-France and called Mimi within the family. Her maternal grandfather, François Blanc, had left an estimated fortune of FF 88M when he died in 1877. However, his widow, born Marie Hensel, left mostly debts for her three children, including Marie's mother Marie-Félix, to pay off upon her death in July 1881. Prince Roland protected his wife's fortune by persuading her to renounce that of her late mother before the amount of her debts became known. Marie-Felix died of an embolism shortly after Marie's birth, leaving half of her FF 8.4M dowry to her husband and half to her daughter. Most was managed in trust during Marie's youth by her father, who had few financial resources of his own. Marie lived with her father, a published geographer and botanist, in Paris and on various family country estates where he studied, wrote and lectured, leading an active life in Parisian academic circles and on expeditions abroad, while her daily life was supervised by tutors and servants. Affected by phobias and hypochondria as a youth, Marie spent much of her time in seclusion, reading literature and writing the personal journals which reveal her inquisitive spirit and early commitment to the scientific method reflected in her father's scholarship.

Several candidates for future husband presented themselves or were considered by Prince Roland for his daughter's hand, notably a distant cousin of the princely House of Murat, Prince Hermann of Saxe-Weimar-Eisenach and Louis II, Prince of Monaco. Following a Parisian luncheon Prince Roland hosted for King George I of Greece in September 1906, the king agreed to the prospect of a marriage between their children. Prince George of Greece and Denmark, second of the king's five sons, was introduced to Marie on 19 July 1907 at the Bonapartes' home in Paris. Although homosexual, he courted her for twenty-eight days, confiding that from 1883, he'd lived not at his father's Greek court in Athens, but at Bernstorff Palace near Copenhagen with Prince Valdemar of Denmark, his father's youngest brother. The Queen had taken the boy to Denmark to enlist him in the Danish royal navy and consigned him to the care of Valdemar, who was an admiral in the Danish fleet. Feeling abandoned by his father on this occasion, George described to his fiancée the profound attachment he developed for his uncle. He admitted that, contrary to what he knew were her hopes, he could not commit to living permanently in France since he was obligated to undertake royal duties in Greece or on its behalf if summoned to do so.

Once his proposal of marriage was accepted, the bride's father was astonished when Marie's fiancée Prince George waived any contractual clause guaranteeing an allowance or inheritance from Marie; she would retain and manage her own fortune (a trust yielding 800,000 francs per annum, her father leaving 60 million francs on his death in 1924) and only their future children would receive legacies. The approximate value of Marie's 800,000 franc annuity was equivalent to £32,000 in November 1907, (equivalent to £4,275,908 in 2023) whilst her father's estate of 60 million francs equated to some £711,000 in 1924 (equivalent to £51,221,730 in 2023).

Marie's mother had reportedly brought her husband a dowry worth 8,400,000 francs in 1880, as well as a reversionary right to a further 6,000,000 francs which she would receive after her mother's death.

On 21 November 1907 in Paris, Marie and George were married in a civil ceremony, with a subsequent Greek Orthodox ceremony on 12 December 1907, at Athens. Thereafter she was known as Princess George of Greece and Denmark.

By March 1908 Marie was pregnant and, as agreed, the couple returned to France to take up residence. When George brought his bride to Denmark for the first visit with his uncle, Prince Valdemar's wife, Marie d'Orléans, was at pains to explain to Marie Bonaparte the intimacy which united uncle and nephew, so deep that at the end of each of George's several yearly visits to Bernstorff he would weep, Valdemar would fall sick, and the women learned the patience not to intrude upon their husbands' private moments. During the first of these visits, Marie Bonaparte and Valdemar found themselves engaging in the kind of passionate intimacies she had looked forward to with her husband who, however, only seemed to enjoy them vicariously, sitting or lying beside his wife and uncle. On a later visit, Marie Bonaparte carried on a passionate flirtation with Prince Aage, Count of Rosenborg, Valdemar's eldest son. In neither case does it appear that George objected, or felt obliged to give the matter any attention. Marie Bonaparte came to admire the forbearance and independence of Valdemar's wife under circumstances which caused her bewilderment and estrangement from her own husband.