Rainier III, Prince of Monaco

Rainier III, Prince of Monaco (1923–2005) ruled the small Mediterranean principality from 1949 until his death in 2005, a reign of 56 years that made him one of the longest-serving monarchs in modern European history. Born Rainier Louis Henri Maxence Bertrand Grimaldi in the Prince's Palace, he was the grandson of Prince Louis II and inherited a state recovering from the German occupation of World War II.

During the war Rainier served in the French army, taking part in the Alsace campaign in 1944 and 1945; he received the Croix de Guerre and the Bronze Star for his service. He ascended the throne on 9 May 1949 and quickly turned his attention to modernizing Monaco's economy, expanding banking, real estate, and tourism beyond the older reliance on the casino at Monte Carlo.

His 1956 marriage to the American film actress Grace Kelly drew global attention to Monaco and produced three children: Caroline, Albert, and Stéphanie. Princess Grace's death in a 1982 car accident on a road above Monaco was a private and public blow from which the prince was widely said never fully to recover.

Rainier's later decades saw a long dispute with French president Charles de Gaulle over taxation and sovereignty, resolved by treaty in 1963, and major land-reclamation projects that physically enlarged the principality. He was succeeded on his death by his son Albert II.

The name Rainier is a French and Germanic masculine given name from the Old Germanic Raginhari, combining ragin meaning counsel and hari meaning army, so roughly wise warrior or counsel-army. He carried the name as the third Monégasque prince to bear it.