Brooke Astor, who by night reigned over New York society with a disdain for pretension and by day devoted her time and considerable resources to New York’s unfortunate, died this afternoon at her weekend estate, Holly Hill, in Briarcliff Manor, N.Y. She was 105.

Her death was confirmed by Kenneth E. Warner, a lawyer for Mrs. Astor’s son, Anthony D. Marshall.

Mrs. Astor’s image as a benevolent society matron was overshadowed last year by that of a victimized dowager at the center of a very public family battle over her care and fortune.

Yet for decades she had been known as the city’s unofficial first lady, one who moved effortlessly from the sumptuous apartments of Fifth Avenue to the ragged barrios of East Harlem, deploying her inherited millions to help the poor help themselves.

Among the rich of New York, she was perhaps the last bridge to the Gilded Age, when “society” was a closed world of old-money families, the so-called Four Hundred, ruled over by a grandmother of Mrs. Astor’s by marriage, Mrs. William Backhouse Astor.

But it was a changing social order that Brooke Astor oversaw. Hers was a society defined more by balance sheets than bloodline. It opened its doors to entrepreneurs and Wall Street movers and shakers who had bought entree with so many millions that in the 1980s Mrs. Astor declared herself “nouveau pauvre.”

Although aristocratic in upbringing, style and social milieu, she never sought to be the arbiter of society that the Astor name might have entitled her to be. She never wanted to rule over a world that she was among the first to recognize was no more.

And in her advanced age, her own world seemed to collapse as well. In a startling episode that played out in court and on the front pages of the city’s newspapers last year, one of her grandsons, Philip Marshall, accused her only son of neglecting her care and exploiting her to enrich himself and his wife.

Although Anthony Marshall vigorously denied the accusations, the public was suddenly given a picture of Mrs. Astor as a mistreated centenarian. By the grandson’s account, she had been stripped of her dignity and some of her favorite art, denied medicine and the company of her two dogs, Boysie and Girlsie, and forced to sleep in chilly misery on a couch smelling of urine.

The dispute stretched over months, its every wrinkle making headlines. Then, on Oct. 13, the parties announced a settlement, avoiding what could have been a costly and sensational trial. In December a State Supreme Court judge overseeing the legal battle said that the claims of elder abuse had not been substantiated.

Her close friends said her declining physical condition left her unaware of the tumult, but it was a bitter and unlikely last chapter for a woman who had defined high society and made philanthropy her career for almost four decades.

She took up that vocation after her third husband, Vincent Astor, heir to the fur and real estate fortune of John Jacob Astor, died and left about $60 million to her personally and an equal amount for a foundation “for the alleviation of human suffering.” Her husband had told her, “You’ll have fun, Pookie.”

In fact, she said she had a great deal of fun giving money away. With a wink and a sly smile, she liked to quote the leading character in Thornton Wilder’s play “The Matchmaker,” saying, “Money is like manure; it’s not worth a thing unless it’s spread around.”

It was Mrs. Astor who decided that because most of the Astor fortune had been made in New York real estate, it should be spent in New York, for New Yorkers. Grants supported the city’s museums and libraries, its boys’ and girls’ clubs, homes for the elderly, churches, landmarks and other institutions and programs.

She made it her duty to evaluate for herself every organization or group that sought help from the Vincent Astor Foundation. In her chauffeur-driven Mercedes-Benz, she traveled all over New York to visit the tenements and churches and neighborhood programs she was considering for foundation grants. Many times a welcoming lunch awaited her on paper plates and plastic folding tables set up for the occasion. She would exclaim over what she called the “delicious sauces”: deli mustard and pickle relish.

Socialite With a Common Touch

At night — almost every night, even into her 90s — she could be found surrounded by crystal and caviar, done up in her designer dresses and magnificent jewels, seated to the right of the host. (She was always seated to the right of the host.)

If she nurtured a playful and sometimes wicked eye for the manners of high society (she once said that “unlike Queen Victoria, we are amused — we are always amused”), she made a point of showing her appreciation for people who worked to help the needy. She always “made an effort,” to use a phrase of the upper class.

For her forays around the city, she dressed as she did when she joined the ladies who lunch at East Side bistros: a finely tailored suit or a designer dress, a hat in any weather, a cashmere coat when it was cool and, in her last years, an elegant cane, her one apparent concession to age. She always wore a ring of precious stones, a bracelet, a brooch and earrings.

“If I go up to Harlem or down to Sixth Street, and I’m not dressed up or I’m not wearing my jewelry, then the people feel I’m talking down to them,” she said. “People expect to see Mrs. Astor, not some dowdy old lady, and I don’t intend to disappoint them.”

She could talk to anyone as she made her rounds, offering encouragement to a child working at a library computer, counseling a mother about the importance of reading. To a janitor pushing a broom at a branch library — and she tried to visit every branch — she might give a word of thanks “for keeping this place so clean.” She was thrilled when theBronx Zoo named a baby elephant Astor in her honor, delighted when a baker at a market the foundation supported pressed two loaves of bread on her.

When the Astor Foundation closed its doors in December 1997, Mrs. Astor had overseen the disbursement of almost $195 million, almost all within New York City. Although the foundation was not large compared with powerhouses like Ford, Rockefeller and Carnegie, its contributions often served as seed money: others followed, knowing that if Mrs. Astor had given her seal of approval to a cause, it was worthy of support.

As she neared 99, she said she was glad she had not lived in the kind of indolence her fortune would have allowed. She had had fun helping the needy, she said. If she regretted anything, she said, it was that she had not visited friends in Europe often enough and that she had not been able to read, and write, all the books she would have wished.

She was slight of build, somewhat frail and very thin in her last years, but her hair remained honey-colored, and she liked to boast, although it was widely doubted, that she had never had a face-lift. She kept fit well into her advanced years by swimming 1,000 strokes each weekend day and nearly every day in summer, even in the chilly waters that surrounded her house in Northeast Harbor, Me. Every year she liked to march behind the fire engine in Northeast Harbor’s Memorial Day parade, waving a little American flag.

Even into her 90s, she loved to go out, especially to places where there would be dancing. “When that music starts,” she said, “it enters my blood like a fever.” When she stayed home, she would have people in. An invitation to one of her small luncheons or dinners — especially if it was for a first lady, like her friend Nancy Reagan — was a sign of having arrived at the highest level of society.

When Mrs. Astor slowed down, it was often at Holly Hill, her 68-acre weekend estate. “It’s like backing up to the Esso and getting refueled,” she once said. “I love people, but I couldn’t do it seven days a week.”

In her 98th year she was still writing articles for Vanity Fair magazine, noting with regret, for example, that gentlemen no longer wore hats and that women no longer flirted, something she said she herself never failed to do.

If she had any weakness, it was for her dogs. She always had several and called them her “lovey babes.” She loved Henry O. K. Astor, a dachshund, even after he bit off a piece of her middle finger.

Mrs. Astor spent a good deal of her time in the boardrooms of the Metropolitan Museum of Art, the Morgan Library & Museum, Rockefeller University and other prestigious cultural centers. A trustee of each, she worked with curators and other staff members. She finally devoted herself almost exclusively to the New York Public Library.

Vartan Gregorian, who was president of the library when Mrs. Astor took it as her main cause, observed then that Mrs. Astor stood apart from her class. “She is of them, but not part of them,” said Mr. Gregorian, who is now president of the Carnegie Corporation of New York. “She’s not dominated by the same considerations many socialites are.

“Hers is not a socialite’s attitude,” he went on. “She is genuinely concerned. There’s a lot of effort and mental discipline. She’s one of the few who have read so much. She’s a teacher; she teaches by example, by analogy. If you spend an evening with Brooke Astor and come away empty, there’s something wrong with your antennae.”

The Early Years

Brooke Russell was born in Portsmouth, N.H., on March 30, 1902. She remembered a childhood that was secure and happy, if often solitary. She had no siblings and spent much of that time in foreign lands. One of her earliest memories was of standing on her bed saluting as a marine bugler outside played during a flag-raising at the American legation in Beijing, where her father, Maj. Gen. John H. Russell, was commander of the guard. (She remembered that the bugler’s name was Johnny Malone, and that she had loved him.)

Her father, who later became commandant of the Marine Corps, also took the family along when he was assigned to Hawaii and Panama. She remembered her mother, Mabel Howard, as beautiful and flirtatious and said that patriotism ran in the family on both sides.

Mrs. Astor kept the diaries, letters and drawings from her childhood travels squirreled away in Briarcliff Manor in a closet that she called her “archive room.” Some of her early drawings, poems and plays were reproduced in an illustrated edition of “Patchwork Child: Early Memories,” published in 1993.

“I’ve been scribbling all my life,” she said. Her writing came to include many magazine articles, two published volumes of autobiography — a 1962 edition of “Patchwork Child” and “Footprints” (1980) — and two novels, “The Bluebird Is at Home” (1965) and “The Last Blossom on the Plum Tree: A Period Piece” (1986).

What she remembered as an idyllic childhood ended abruptly, she said, when, at age 16, she was invited to the senior prom at Princeton to fill in for a girl who had fallen ill. There she met J. Dryden Kuser. Her mother, she said, was “dazzled” by Mr. Kuser’s substantial fortune. After a brief courtship, he asked Brooke to marry him, and though she felt unprepared for marriage, she said, she reluctantly agreed.

“Dryden promised me my own house, all the dogs I wanted, and a car as soon as I was old enough to have a driver’s license,” she said.

Married Life, Times Three

They married in 1919, and for 11 years they lived in great luxury and considerable misery. Her merry nature gradually darkened as the marriage headed for disaster in every respect except for the birth of her son, Anthony. She and Mr. Kuser divorced in 1930.

Her second marriage, two years later, to Charles Marshall, known to everyone as Buddie, brought her 20 years of happiness. Mr. Marshall, she said, was the love of her life. She wrote that her son admired him so much that he adopted his last name as his own.

Charles Marshall died suddenly in 1952, leaving Mrs. Astor without an inheritance. She took a job at House & Garden, a Condé Nast magazine, where she had previously worked.

Not long afterward, still in mourning, she met Vincent Astor at a dinner. A month later, he proposed. She described the scene in “Footprints”: “I couldn’t believe my ears. ‘But you hardly know me,’ I said. ‘We really don’t know each other at all.’

“ ‘I know a lot about you,’ Vincent answered. ‘And I can swear on the Bible that if you marry me I will do everything I possibly can to take care of you and make you happy — and earn your love.’ Well, such suddenness would have thrilled me and elated me at 20, but in my late 40s, I was frightened by it.”

Within months, however, she became his third wife, in 1953. She had, perhaps, been right to hesitate. Vincent Astor, she said, was a suspicious man who thought everyone wanted something from him. As a result, the couple were often alone. She said she lost contact with her friends. He even asked her not to chat on the telephone when he was at home. But she tried to make him cheerful, she said, playing the piano for him and amusing him.

The marriage was brief. In five and a half years, Mr. Astor was dead, leaving his millions for her and for the foundation. “After Vincent died, I recreated myself,” she said, referring to her decades of philanthropy at the Vincent Astor Foundation. “Now I feel I’ve become a public monument,” she said during one of many meetings and interviews since the 1980s.

A Living Landmark

She was, in fact, named a living landmark by the New York Landmarks Conservancy, which said in 1996 that “a list of the city monuments is incomplete without her name alongside.” At bicentennial celebrations in 1976, the Municipal Art Society of New York had a medal struck in bronze to proclaim her achievements. Mayor Abraham D. Beame said Mrs. Astor had done more for New York than any other person.

The Astor Foundation’s annual reports had become a Baedeker to the city, showing important contributions to what she called New York’s “crown jewels”: the Metropolitan Museum of Art, the Morgan Library and the New York Botanical Garden, as well as theCornell University Medical College, Rockefeller University, the New York Zoological Society (now the Wildlife Conservation Society), the South Street Seaport and many others.

In 1977, when Mrs. Astor made the New York Public Library her primary cause, the Astor Foundation offered a $5 million matching grant if the library could raise $10 million. She then went out to help raise the $10 million. The main entrance of the research library at Fifth Avenue and 42nd Street was named Astor Hall in her honor. At the Metropolitan Museum of Art, she took a particular interest in the construction of the Chinese courtyard and scholar’s room, which was named Astor Court.

But having her name on a wall was never much of a priority. Foundation money often went for necessities the public never knew anything about. There was no Astor name affixed to things like air-conditioning or a staff lunch room at one institution or another.

Astor money went to provide new windows for a nursing home on Riverside Drive, fire escapes for a homeless residence in the Bronx, a boiler for a youth center in the Williamsburg section of Brooklyn and vest-pocket parks around the city. The foundation was among the first to support neighborhood and community-based development projects as well as jobs programs. Grants, to name a few, also went to institutions then known as the Cooper-Hewitt Museum, the National Academy of Design and Columbia College as well as Carnegie Hall, Central Park, the Museum of Natural History, Ellis Island and the Animal Medical Center, to care for the pets of the elderly poor.

“Old people have old pets,” she said. “It’s a wonderful place. When I’m sick, that’s where I want them to take me.”

A Family Divided

Mrs. Astor remained at her Park Avenue duplex apartment as age and infirmity overtook her. Though she made occasional social appearances in her last years — David Rockefellergave her a 100th birthday party at the Rockefeller family’s Hudson Valley estate in 2002 — she had become all but a recluse toward the end.

Then, in July, came the astonishing news that Philip Marshall had sued his father, Anthony Marshall, accusing him of stripping Mrs. Astor’s apartment of artwork to enrich himself and neglecting her in ways that threatened her health and safety.

Philip Marshall enlisted the help and affidavits of Annette de la Renta, Mrs. Astor’s friend of more than 45 years, as well as Mr. Rockefeller, Henry A. Kissinger and others as he sought to wrest control of Mrs. Astor’s affairs from his father.

Anthony Marshall, 83, a Broadway producer and former diplomat who once worked for the Central Intelligence Agency, said the accusations were “completely untrue.”

Under the settlement, he and his wife, Charlene, admitted no wrongdoing, but both were required to give up their roles as co-executors of Mrs. Astor’s estate, and Mr. Marshall agreed to cease being steward of his mother’s health care and financial affairs. They also were required to rescind the transfer of Mrs. Astor’s Maine estate to themselves.

The settlement stipulated that JPMorgan Chase & Company and Mrs. de la Renta would be her permanent guardians. Mrs. de la Renta quickly moved Mrs. Astor from New York to her beloved estate in Briarcliff Manor and was said to have visited her regularly. The bank, which had overseen Mrs. Astor’s finances since the court filing in July 2006, agreed not to pursue litigation to recover millions of dollars in cash, property and stocks that it believed Mr. Marshall might have improperly obtained while managing his mother’s holdings.

Any future legal claims against Mr. Marshall, the settlement said, were to be dealt with in Surrogate’s Court on Mrs. Astor’s death and left to the discretion of the executor of her estate, to be named by a judge.

Besides her son, Anthony, of New York, and her grandson Philip, of South Dartmouth, Mass., Mrs. Astor is survived by another grandson, Philip’s twin brother, Alec.

A widow for 48 years, Mrs. Astor had a number of suitors in that time but did not want to marry again. “I just don’t want anyone tugging at my sleeve at 10 o’clock telling me it’s time to go home,” she once told her friend Marietta Tree. “I want to go at my own speed, and it’s a lot faster than theirs.”

But she remained open to new friends. She used to say that each year she took on one new friend to replace an old one who had died. While Mrs. Astor lost track of some of those friends over the years, she regretted the misunderstandings that arose from time to time. When she was 98, she recalled with satisfaction that she had telephoned a man who had once made her so angry that she had stopped talking to him. The call was to compliment him on an article he had written. “I want to be at peace with all of my friends when I die,” she said.

Roberta Brooke Russell Astor