Born in Monaco as Prince Louis Henri Maxence Bertrand, Rainier was scion of a Genoese family whose control of Monaco dates back to medieval wars between two Italian factions, the Guelphs and the Ghibellines. He was the 30th descendant of Otto Canella, who founded the house of Grimaldi.

The Grimaldis, aligned with the pro-papal Guelphs, were forced out of Genoa, but on a January night in 1297, they had their revenge. Francois Grimaldi disguised himself as a monk and was admitted through the gates of the fortress perched on a rock high above the Mediterranean. With a sword concealed in his habit, he overpowered the guards and admitted his company of triumphant Guelph troops into Monaco.

The Grimaldis took control of what today is a 482-acre principality -- smaller than New York City's Central Park -- wedged between France, Italy and the sea. Except for brief periods, they have ruled ever since.

The young prince was educated in England, at the Summerfield College in Saint Leonards on Sea and at Stowe School at Buckingham. He also studied at the Chateau de Rosey College at Rolle, Switzerland, and received a bachelor's degree at the School of Political Sciences in Paris.

In 1944, he enlisted as a foreign volunteer in the French Army. He served with the 2nd Army, participated in operations for the Alsace campaign and was decorated with the Croix de Guerre with bronze star.

After the war, he was assigned to the French Military Mission in Berlin, becoming a captain in 1949 and a colonel in 1954. He also was the commandant of the Monagasque carabinieri, Monaco's standing army.

Rainier assumed the throne in 1949, five years after his mother, Princess Charlotte, took up with a notorious jewel thief known as Rene the Walking Stick and renounced her claim. His father was Prince Pierre Grimaldi of the House of Polignac, whom Charlotte married in 1920 and divorced in 1930.

Prince Louis II, Rainier's grandfather, bestowed the right of rule on young Rainier in 1949 after being extremely ill for several months. Louis died a few weeks later.

The prince was considered the most eligible bachelor in Europe when he assumed the throne just before his 27th birthday. Tabloids and gossip columns linked him with French actress Gisele Pascal, popularly labeled "the uncrowned princess of Monaco." But his spiritual adviser and chaplain, Father Richard Tucker of Wilmington, Del., known as "Father Tuck," broke up the twosome and ruled out the possibility of marriage.

"Only away from the principality can His Highness be more a good fellow than a prince," Tucker told The Washington Post in 1956. "At Monaco he is and must be more a prince than a good fellow. He never participates in anything in any way lacking in dignity among his own people. To swim and dance, he leaves the principality."

In a spate of pre-marriage profiles, Rainier was described as "blue-eyed, dark-haired, of medium height and athletic, speaks English with only the trace of a continental accent and smiles charmingly." He was a "remarkably sea-conscious man" who liked sailing and living aboard his 150-foot yacht. He also enjoyed making undersea movies and collecting rare animals for his private menagerie. He owned nine dogs and told reporters he intended to tame his captive lions personally.