Polly Lauder Tunney, a Connecticut socialite and Carnegie heiress whose secret romance and subsequent marriage to the former heavyweight champion Gene Tunney was one of the most sensational love stories of the 1920s, died Saturday at her home in Stamford, Conn. She was 100.

Her death was confirmed Monday by her son John V. Tunney, the former United States Senator from California. His mother had had several strokes in recent years, including one about a week ago, he said.

For Mrs. Tunney, who had grown up in a world of wealth and privilege reaching from Greenwich, Conn., to Versailles, meeting and falling in love with a prizefighter, even a famous one, seemed unlikely. But Gene Tunney was no ordinary prizefighter.

Though he had grown up relatively poor in Greenwich Village as the son of Irish immigrants — his father was a longshoreman — Tunney, a high school dropout, had developed an insatiable appetite for classical literature, especially the works of Shakespeare. Handsome and articulate, he lectured on Shakespeare at Yale and befriendedGeorge Bernard Shaw, Thornton Wilder and other writers, earning the scorn of the boxing establishment and many boxing fans.

Polly Lauder, a striking beauty, met Tunney shortly before he won the heavyweight title from Jack Dempsey in one of the most stunning upsets in boxing history on Sept. 23, 1926. Tunney had originally been introduced to Miss Lauder’s older sister, Katherine Dewing, by a longtime friend, Samuel Pryor Jr., who also lived in Greenwich.

Katherine Dewing in turn arranged for Tunney and her sister to meet at a dinner party that Mrs. Dewing and her husband gave at their Manhattan apartment. Over the next two years, a romance blossomed, though only a few close friends and relatives knew about it.

In August 1928 — less than a month after the last fight of Tunney’s career, a technical knockout of the New Zealander Tom Heeney — Polly’s mother, Katherine Lauder, announced from the family’s summer home on Johns Island, off the coast of Maine, that Polly and Tunney had become engaged. (Tunney had promised Miss Lauder that he would quit boxing after fulfilling his contractual obligations, which included the Heeney fight and, earlier, a rematch with Dempsey, a fight that became memorable as Tunney’s “long-count” victory.)

The engagement was front-page news across the country and touched off a frenzy by reporters and photographers eager to interview the couple. “Wedding Gong Calls Gene,” declared a headline in The Los Angeles Times. But the couple remained out of public view.

In September they went to Europe, separately, and were married in a small ceremony in a hotel in Rome on Oct. 3, 1928. She was 21 when they wed. The New York Times said the scene after the wedding “looked mighty like a riot” as clothes were torn and cameras smashed in a melee of photographers jostling to capture images of the couple.

After spending 14 months traveling in Europe, the Tunneys returned to the United States and moved into a house in North Stamford built in 1742 and began restoring it. Known as Star Meadow Farm, the house sits on 200 acres, where the Tunneys raised Hereford cattle and sheep.

Tunney, who had little to do with boxing after he retired as the undefeated heavyweight champion July 31, 1928, became a successful businessman in New York. He died in 1978 at 81.

Born Mary Josephine Lauder in Greenwich on April 24, 1907, and known since childhood as Polly, Mrs. Tunney was the granddaughter of George Lauder, a first cousin of Andrew Carnegie, with whom he had grown up in Scotland. An engineer, Lauder became, in his 30s, a confidential adviser to Carnegie and a director and shareholder of the Carnegie Steel Company in Pittsburgh shortly after Carnegie founded it in the 1870s.

Lauder’s son, George Jr., inherited much of his father’s fortune and became a well-known yachtsman, owning a 136-foot two-masted schooner. He was a director of Presbyterian Hospital and the Manhattan Ear and Eye Hospital in New York and died of influenza at 37, leaving a fortune estimated at $50 million to his wife and to his children, Polly, Katherine and George III.

After attending private schools in Greenwich, Polly Lauder graduated from the Lenox School in New York and the Finch School in New York and Versailles. She was an accomplished equestrian, sailor and swimmer and remained vigorous into her 90s, driving a car until age 93. A patron of the arts, she was a former vice president of the Metropolitan Opera Guild and a major benefactor of the Audubon Society and the Wildlife Federation.

In addition to her son John, of New York, Mrs. Tunney is survived by two other sons, Gene, of Hawaii, and Jonathan, of New York and Roxbury, Conn.; a daughter, Joan Tunney Cook, of Omaha, Ark.; 10 grandchildren and 9 great-grandchildren.

Mary L Tunney