Prince Rainier III of Monaco, who chose an American film star to be his princess, died early yesterday, almost 49 years after his storybook wedding to Grace Kelly put his tiny Mediterranean principality on the map. He was 81 years old and had reigned for more than 50 years.

He had suffered from heart and kidney problems and was in intensive care for the last few weeks.

His Serene Highness, as he was styled, ruled as a virtual dictator over a sleepy 384-acre principality that, despite its gambling casino and renowned beach club, had failed to regain the once-upon-a-time grandeur it had before World War II. But in 1955, Rainier of the house of Grimaldi, who held more titles than any other crowned head in Europe, journeyed across the sea to America and returned with the hand of Grace Kelly of Philadelphia, the cool, blond film star who had won fame in patrician, even aristocratic roles opposite some of Hollywood’s most illustrious leading men.

The royal wedding in Monte Carlo in April 1956, attracted more than a thousand news reporters whose tales of the event whetted the appetites of travelers to see the picturesque land where a Prince and his Princess were to live happily ever after in a castle and their loyal subjects lived in a never-never land where there was no income tax, no inheritance tax, no capital gains tax, no compulsory military service, and virtually no unemployment.

Until he met Miss Kelly Rainier – a not-very-tall monarch whose waist thickened as the years passed – had been a reluctant bridegroom who seemed to prefer thoroughbred horses, fast cars, skin-diving in shark-infested waters, skiing the most daunting of slopes, and hunting wild boar to marriage. A succession of elegant women kept this daredevil of a prince company while he warded off domesticity until he was 32 years old. But a 1918 treaty required that he produce an heir in order to maintain Monaco’s independence from France, and he acknowledged as much to an interviewer when he said, “I consider it a duty to my people to get married, but a man also must be true to himself by taking a wife he loves.”

At last, Miss Kelly seemed to meet the royal requirements. Within a year of their marriage the birth of a daughter, Caroline Louise Marguerite, assured the continuation of the Grimaldi dynasty and Monaco’s existence as an independent principality. When Albert Alexander Louis Pierre was born in 1958, he superseded his older sister to become heir to the throne. Another daughter, Stephanie, was born in 1965. Rainier leaves seven grandchildren; four from Caroline and three from Stephanie.

Princess Grace became more than a wife and mother. She was the best public relations officer the prince could have hoped for, not only with his own people but with the world at large. Her very presence revived a principality which was being transformed by the prince and his princess from a playground for the wealthy into a less exclusive and more crowded Mecca for tourists eager to try their luck at the gaming tables.

When the princess died in 1982, reportedly from a stroke while she was driving on a mountain road, there was speculation that the prince might abdicate in favor of his son. “I’ve always said that I don’t want to drag on,” he told an interviewer. Of Albert, he said, “He’s young, he’s got plenty of stamina and will, and he knows the place well. He was born here, educated here, so I think the day he feels ready, why not? I don’t believe in making him wait until I die off.” But Rainier remained on the throne while Albert, not unlike his father before him, pursued other interests for so long that for a while he came to be called “Albert the Unready.” Albert was serving as regent during his father’s last illness and was with him at the time of his death. He is unmarried and has no children. The laws of Monaco were changed in 2002 to allow his sisters and their children to succeed him, though that law has still to be ratified by France.

Prince Rainier Louis Henri Maxence Bertrand was born May 31, 1923. His father was Prince Pierre, Comte de Polignac. His mother was Charlotte, the “love child” of Prince Louis II of Monaco and Juliette Louvet, who was said to have been a laundress in Algeria. Charlotte was legitimized in 1919 and four years later bore the heir to the throne, thereby assuring the principality’s continued independence from France for another generation.

The young prince was sent to England where he attended Summerfields, Hastings, and the Stowe School and later went to Le Rosey in Switzerland and the University of Montpelier in France. A lonely child, he became caught up in the domestic quarrels of his parents when his mother ran off with an Italian doctor and his father sued for divorce in 1930. In 1937, when he was 13 years old, Rainier was given into the custody of his maternal grandfather, Louis II of Monaco, remembered as a hard-drinking sergeant in the French Foreign Legion who married for the first time when he was 75 years old.

His daughter Charlotte renounced her rights to the succession in 1944 in favor of her son, Louis. When Louis II died in 1949, Rainier – officially known as Rainier III – succeeded to the throne, his investiture attended by the entire armed forces of Monaco: 80 infantrymen and 40 firemen. He became the 31st hereditary ruler of Monaco and the possessor of 139 hereditary titles including two princedoms and four dukedoms.

During World War II, the young prince volunteered in the Free French forces and presented himself to the head of his unit, his jacket open and looking most unmilitary. “Lieutenant Rainier Grimaldi reporting,” he said, saluting with one hand, keeping the other in a pocket. “You act as if you joined the army yesterday,” the commanding officer said. “Sorry sir,” said Rainier, “I joined this morning.” But later he traveled behind enemy lines to report on action in the Battle of the Bulge and was awarded the Croix de Guerre with a bronze star.

For a time, Prince Rainier was known as the most ill-tempered monarch in Europe, and he did not hesitate to invoke his royal prerogatives. In 1959, he suspended the Constitution when he felt it inhibited his powers. He also dissolved the National Council and replaced it, in 1961, with a national assembly. In 1962 he reestablished the National Council and granted a new, more liberal constitution that gave women the right to vote. That same year he stood up to President Charles de Gaulle when the French president demanded that Monegasques pay French income taxes or face an economic blockade. A compromise was reached the next year by which French citizens with less than five years residence in Monaco were taxed at French rates and companies doing more than 25% of their business outside the principality were required to pay taxes.

There was no compromise with Aristotle Socrates Onassis, who had bought a majority position in the Societe des Bains de Mer, the delicate but somewhat imprecise name given to the corporation that owned the casinos and some of Monaco’s major hotels and real estate. The Greek shipping tycoon, who kept his yacht parked in the harbor at Monaco, had put himself in a strong position to oppose the business-minded prince’s plans to attract less aristocratic, less blue-blooded tourists. So influential had Mr. Onassis become that the prince started referring to Monte Carlo as Monte Greco.

By 1967, the prince had had enough, and with the reasonably simple ploy of issuing new shares in the Societe des Bains de Mer, Rainier outfoxed his Greek rival and bought him out. There followed an enormous building boom which the British magazine the Economist described as “a game virtually without rules.” The little country could not expand outward so it expanded upward as foreigners – five times as many of them as Monegasques – took up residence in a crime and tax-free haven. High-rises that afforded a view of the sea one day were eclipsed the next by other high-rises built closer to the water’s edge. Similarly, the aristocrats of Europe were soon elbowed out by tourists headed for the slot machines and roulette tables.

Before the royal marriage, Rainier’s name had been linked to various actresses and princesses in Europe. He had a long relationship with Gisele Pascal, a French actress. When he introduced her to the Rev. J. Francis Tucker, an American priest who had come to Monaco to set the prince on the straight and narrow path, and asked what the prelate thought of her, he replied, “I think she’s just fine. She’s a real number. In fact, I could go for her myself.”

“What do you mean, you could go for her yourself?” asked Rainier, “You’re a priest.”

“Well, you’re a prince and you can’t go for her either,” the chaplain snapped.

Rainier ran the little country with an iron hand that included police-state methods of surveillance. The Monaco that Somerset Maugham had once described as “a sunny place for shady people” became a place where suspicious-looking characters – and young men with long hair were sometimes put in that category – were not welcome. If the prince was successful with his principality, he was less so with his children, who tended toward a certain amount of wayward rebelliousness that brought unwelcome headlines.

The press, whose stories had so popularized Monaco at the time of the wedding of Rainier and Grace, were no more popular with the prince than the hippies he shunned. When Princess Caroline married her first husband, Philippe Junot, in civil and religious ceremonies, Variety retaliated for the exclusion of reporters with a two-line notice in the marriages column: “Caroline Grimaldi to Philippe Junot, June 28th and 29th, Monte Carlo. She’s the daughter of former film actress Grace Kelly and casino operator Rainier Grimaldi.”