Born in Monaco on the 31st of May 1923, the only son of Prince Pierre of Monaco, Duke of Valentinois and his wife, the Monegasque Hereditary Princess, Charlotte, Duchess of Valentinois.
Rainier was the first native-born hereditary prince of Monaco since Honore IV in 1758. Rainier’s mother was the only child of Prince Louis II of Monaco and Marie Juliette Louvet; she was later legitimized through formal adoption and subsequently named heir presumptive to the throne of Monaco.
Rainier’s early education was conducted in England, at the prestigious public schools of Summerfields in St Leonards-on-Sea, Sussex, and later at Stowe, in Buckinghamshire.
After England, Rainier attended the Institut Le Rosey in Rolle and Gstaad, Switzerland from 1939, before continuing to the University of Montpellier in France, where he obtained a Bachelor of Arts degree in 1943, and finally to the Institut d’études politiques de Paris in Paris.
In 1944, upon his 21st birthday, Rainier’s mother renounced her right to the Monegasque throne and Rainier became Prince Louis’s direct heir.
In World War II Rainier joined the Free French Army in September 1944, and serving under General de Monsabert as a second lieutenant, and seeing action during the German counter-offensive in Alsace.
He received the French Croix de Guerre with bronze star (representing a brigade level citation) and was given the rank of Chevalier in the French Legion of Honor in 1947.
Following his decommission from the French Army, he was promoted by the French government as a captain in April 1949 and a colonel in December 1954.
In 1979, Rainier made his acting debut alongside Grace in a 33-minute independent film called Rearranged. According to co-star Edward Meeks, after premiering it in Monaco, Grace showed it to ABC TV executives in New York in 1982, who expressed interest if extra scenes were shot to make it an hour long.
Grace’s death precluded this, and the film was never released in any form. On April 19, 1956, Prince Rainier married American actress Grace Kelly after a whirlwind romance.
The couple met at a palace photo shoot and tour while Kelly was attending the Cannes Film Festival.
They had three children—Princess Caroline, Prince Albert II and Princess Stephanie.
What was positioned as a fairy-tale marriage further established Monaco’s reputation as a glamorous playground for the world’s elite.
After his wife’s death, Prince Rainier never remarried. Instead, he threw himself into his work and royal duties.
His children grew up facing scandals of their own through much of their youth and early adulthood. In the final years of his life, Rainier suffered from numerous health-related problems, fueled by his three-pack-a-day cigarette habit.
In May 2014, the film Grace of Monaco premiered at Cannes, starring Nicole Kidman and Tim Roth, portraying the marriage of Kelly and Prince Rainier in 1962.