Rainier III (Rainier Louis Henri Maxence Bertrand Grimaldi; 31 May 1923 – 6 April 2005) was Prince of Monaco from 1949 to his death in 2005. Rainier ruled the Principality of Monaco for almost 56 years.
Rainier was born at the Prince's Palace of Monaco, the only son of Prince Pierre and Hereditary Princess Charlotte of Monaco. He was crucially responsible for the transformation of Monaco's economy, shifting from its traditional casino gambling base to its current status as a tax haven and cultural destination. The Prince also coordinated the substantial reforms of Monaco's constitution, which limited the powers of sovereign rule.
Rainier married American film star Grace Kelly in 1956, which generated global media attention. They had three children: Caroline, Albert and Stéphanie. He died in April 2005 from complications relating to a lung infection as a result of frequent smoking; he was succeeded by his son, Albert II.
Originally elected as a Foreign Member, Prince Rainier became an Honorary Member in the year 2000.
After ascending the throne, Rainier worked to recoup Monaco's lustre, which had become tarnished through financial neglect and scandal (his mother, Princess Charlotte, took a noted jewel thief known as René the Cane as her lover). Upon ascension, the Prince found a treasury that was practically empty. Monaco's traditional gambling clientele, largely European aristocrats, found themselves with reduced funds after World War II. Other successful gambling centres had opened to compete with Monaco. To compensate for the loss of income, Rainier decided to promote Monaco as a tax haven, commercial centre, real-estate development opportunity, and international tourist attraction. The early years of his reign saw the overweening involvement of the Greek shipping tycoon Aristotle Onassis, who took control of the Société des Bains de Mer and envisioned Monaco as solely a gambling resort. Prince Rainier regained control of SBM in 1964, effectively ensuring that his vision of Monaco would be implemented.
During his reign, the Societé Monégasque de Banques et de Métaux Précieux, a bank which held a significant amount of Monaco's capital, was bankrupted by its investments in a media company in 1955, leading to the resignation of Monaco's cabinet. In 1962, Rainier ratified the Principality's new constitution, which significantly reduced the power of the sovereign. He had suspended the previous constitution in 1959, saying that it "has hindered the administrative and political life of the country". The changes ended autocratic rule, placing power with both the Prince and a National Council of eighteen elected members.
At the time of his death, he was the world's second longest-serving living head of state, just below the King of Thailand, Bhumibol Adulyadej.