Princess Grace of Monaco, 52, who won an Academy Award during a brief and dazzling career as an actress and then gave it all up to marry a real prince, died yesterday in Monte Carlo, Monaco, of head injuries suffered in an automobile accident Monday.

As Grace Kelly -- perfectly blond, perfectly made, always patrician, never without a special and tantalizing allure -- she became one of the most admired and sought-after film stars of the early 1950s. In 1956, she married Prince Rainier III of Monaco and settled down in the fabled playland on the French Riviera.

And there she lived in a palace, a princess in fact as well as fancy. She had three children, Crown Prince Albert and the Princesses Caroline and Stephanie. She was admired not only as a star or as a celebrity, but as a woman and the leading lady in a real-life story that nobody really could expect to come true. Although she never made another film after becoming Her Serene Highness, the public never forgot her.

It was, by all accounts, a happy life. She said in an interview last April that she had no fear of the advancing years and no regrets at having left her career.

"I never say 'never' and I never say 'always,' " she said. "But to go back and pick up a career 26 years later seems very unlikely. I did enjoy and take pride in my work as an actress, yet I am bemused by suppositions that my life has since somehow been less fulfilling. That certainly is not the case. Rather the reverse."

The second part of her life -- the part in which the beautiful girl from the Main Line of Philadelphia became the bride of a prince -- might have happened had she never been an actress. But the fact is that it was as an actress -- and a good one -- that she met Prince Rainier. It occurred during the filming of "To Catch a Thief," in which she costarred with Cary Grant under the direction of Alfred Hitchcock. By then, her Hollywood career had reached its zenith.

But that is getting way ahead of the Grace Kelly story. That began on Nov. 12, 1929, when Grace Patricia Kelly was born in Philadelphia. Her parents were John Brendan and Margaret (Majer) Kelly. Her father was an Olympic oarsman who was not permitted to compete at the famous Henley Regatta in England because he had once been a bricklayer.The senior Kelly went on to make a fortune in the construction industry.

His son, Jack, became a rowing champion in his turn and twice won the Diamond Sculls at Henley. Other branches of the family were in front of the footlights. Her playwright uncle, George Kelly, won the Pulitzer Prize for drama for "Craig's Wife." Another uncle, Walter C. Kelly, was famous in vaudeville as the "Virginia judge."

Young Grace Kelly is said to have been shy and subject to asthma and head colds. She was educated at proper schools in Pennsylvania. Her ambition from an early age was to become an actress and it was an ambition that the careers of her uncles and the interests of her parents made it easier to follow. She spent two years at the American Academy of Dramatic Arts in New York, modeled and appeared in summer stock. Her training for the stage was both classical and rigorous.

In 1949, she made her Broadway debut in "The Father," by August Strindberg. The production starred Raymond Massey and ran for two months. Her success brought offers from Hollywood, but she declined to become a mere starlet. Her first film was "Fourteen Hours," in which she had a minor role.

In 1952, she played the Quaker wife of Gary Cooper, the stoic and principled law man in the classic western "High Noon." There followed "Mogambo," (1953) a story set in Africa in which she played an English lady who is part of a triangle. The other two sides were played by Clark Gable and Ava Gardner. For this sometimes steaming performance Miss Kelly was nominated for an Academy Award as best supporting actress of the year.

In 1954, she starred in "Dial M for Murder," the first of the three films she made with Hitchcock. The second was "Rear Window," costarring James Stewart in the role of a photographer who is recovering from a broken leg. He is in danger of losing his life to a psychopath whom he spots through the window of his apartment while he is laid up. Miss Kelly, playing a high-fashion model, was Stewart's fiancee. Consoling him, she moves toward him and says, "Preview of coming attractions." The scene moved Hitchcock to speak of her "sexual elegance."

In 1955, Miss Kelly appeared with William Holden in "The Bridges of Toko-Ri," a film about the Korean war. In one of its memorable scenes, she and Holden are bathing in a communal Japanese bath. They are joined unexpectedly by a middle-aged Japanese couple and there is a moment of sensuality interrupted by shock, which dissolves into innocence and understanding.

And then, with the major studios battling for her services, there was "Country Girl" with Bing Crosby. Her part was that of a disillusioned but iron-willed woman married to an alcoholic. Hardly a glamorous role, the part of one of society's victims, but a role in which Grace Kelly could not be ignored. Indeed, critics thought she was marvelous and she won the Academy Award and the New York Film Critics Award. The world of film lay at her feet.

So did the public. Miss Kelly had five films in theaters in 1955 and four of them were among the box office hits of the year. (The fifth was "Green Fire," a jungle adventure for which Miss Kelly herself had little enthusiasm.) She was voted the second most powerful box-office attraction.

Then came the making of "To Catch a Thief." The filming was on the Riviera and there Miss Kelly met Prince Rainier. The Grace Kelly story was almost over and the Princess Grace story was about to begin. As Grace Kelly, she made "High Society," a musical version of "The Philadelphia Story" with Crosby and Frank Sinatra, and "The Swan," a Ferenc Molnar comedy about the romantic complications of a princess. Alec Guinness and Louis Jourdan were featured with her.

Her marriage, one of the premier social events of the decade, united the Kellys of Philadelphia with the Grimaldis, members of the old European aristocracy and the rulers of Monaco since 1297. It took place in two stages. On April 18, 1956, there was a civil ceremony to satisfy the law. On the following day, the union was sanctified in a splendid ceremony in the Catholic cathedral in Monaco.

It was estimated that 1,500 reporters were assigned to cover the event. Crowds were such that Prince Rainier summoned the assistance of French riot police.

In the years that followed, Princess Grace devoted herself to good works in behalf of the Red Cross, the International Festival of the Arts, the Princess Grace Foundation, which supports the preservation of native arts and crafts, and the World Association of Friends of Children.

In the interview last April, the princess said, "Being a grandmother would be an exciting experience."