Martha Ellis Gellhorn, who as one of the first female war correspondents covered a dozen major conflicts in a writing career spanning more than six decades, died on Sunday at her home in London. She was 89.

Ms. Gellhorn was a cocky, raspy-voiced maverick who saw herself as a champion of ordinary people trapped in conflicts created by the rich and powerful. That she was known to many largely because of her marriage to Ernest Hemingway, from 1940 to 1945, caused her unending irritation, especially when critics tried to find parallels between her lean writing style and that of her more celebrated husband.

''Why should I be a footnote to somebody else's life?'' she bitterly asked in an interview, pointing out that she had written two novels before meeting Hemingway and continued writing for almost a half-century after leaving him.

As a journalist, Ms. Gellhorn had no use for the notion of objectivity. The chief point of going to cover anything, she felt, was so you could tell what you saw, contradict the lies and let the bad guys have it.

''You go into a hospital, and it's full of wounded kids,'' she once said. ''So you write what you see and how it is. You don't say there's 37 wounded children in this hospital, but maybe there's 38 wounded children on the other side. You write what you see.''

Though best known for her groundbreaking journalism, Ms. Gellhorn was also an accomplished fiction writer, author of 5 novels, 14 novellas and 2 collections of short stories, many of which were based on people and incidents she encountered during her prodigious travels.

Fresh out of Bryn Mawr College in 1927, she began writing for The New Republic, then became a crime reporter for a local newspaper in Albany. Ms. Gellhorn got to Europe by writing a brochure for the Holland American Line and traveled throughout the continent. Later, she met Harry Hopkins, President Franklin D. Roosevelt's confidant, and talked her way into a job with the New Deal, wandering America and writing about the effects of the Depression on ordinary people.

She went to Spain in 1937 with nothing but a knapsack and $50, covered the conflict for Collier's Weekly and became Hemingway's lover.

''In Barcelona, it was perfect bombing weather,'' she wrote in a typical dispatch in 1938. ''The cafes along the Ramblas were crowded. There was nothing much to drink; a sweet fizzy poison called orangeade and a horrible liquid supposed to be sherry. There was, of course, nothing to eat. Everyone was out enjoying the cold afternoon sunlight. No bombers had come over for at least two hours.''

She covered the blitz in London. On D-Day, she stowed away on a hospital ship and snuck ashore as a stretcher bearer. She got British pilots to let her ride along on night bombing raids over Germany. When the Allies liberated Dachau, she was there to write about it.

''Behind the barbed wire and the electric fence,'' she wrote of her visit to Dachau, ''the skeletons sat in the sun and searched themselves for lice. They have no age and no faces; they all look alike and like nothing you will ever see if you are lucky.''

She covered Russia's war against Finland in 1939, trekked across China with Hemingway in 1940, and became increasingly critical of the United States, which she saw as a ''colonial power,'' eventually settling abroad for good. She covered Vietnam, Nicaraguan contras, the Arab-Israeli conflict and, at the age of 81, the United States invasion of Panama. It was only when war came to Bosnia that she gave it a pass.

''Too old,'' she said. ''You have to be nimble for war.''

Ms. Gellhorn's war correspondence was collected in ''The Face of War'' in 1959. She always focused on ordinary foot soldiers and civilians, ignoring the generals. Her peacetime journalism was collected in ''The View From the Ground'' in 1988.

Among her novels were ''A Stricken Field'' (1940), set among refugees in Prague just before the Nazi invasion of Czechoslovakia, and ''Liana'' (1944), about the marriage of a mulatto woman and a rich white man in the French Caribbean.

Many reviewers felt Ms. Gellhorn was even more successful as a writer of novellas, and she was highly praised for ''The Weather in Africa'' (1988), three novellas set on that continent, and ''The Novellas of Martha Gellhorn'' (1993).

Ms. Gellhorn sometimes took criticism from political conservatives, who painted her as a left-leaning dilettante whose writing was often didactic and sentimental. Others criticized her vivid journalism as being, stylistically, too much like fiction and her terse fiction as being, stylistically, too much like journalism.

But her longevity and the compelling pull of her life story overrode such criticisms. A heroine to generations of young women correspondents for her fight to get equal treatment and a place on the front lines with male colleagues, she was also a romantic figure for her wartime relationship with one of the century's most famous writers and her subsequent rejection of him.

Ms. Gellhorn's father was a doctor in St. Louis with progressive notions and her mother, whom she adored, was a suffragist and social reformer who sometimes took her daughter with her to rallies and protests.

Her father pulled her out of a convent school when he discovered the nuns were teaching female anatomy with a textbook that had its pictures covered and transferred the girl to a progressive coeducational school of which her mother was a co-founder. Later, at Bryn Mawr, Ms. Gellhorn changed her major from English to French, which became useful for her journalistic work in Europe. In 1934, she was among a group of American students invited to tour Nazi Germany, and she never forgot her first encounter with Fascism. When she returned to the United States and was working for the Federal Emergency Relief Administration, she befriended Eleanor Roosevelt and spent some time, as the First Lady's guest, at the White House. She also wrote a collection of novellas about it, ''The Trouble I've Seen'' (1936).

Her first marriage, in 1933 to Bertrand de Jouvenel, a French pacifist who was the son-in-law of the novelist Colette, ended in divorce.

In 1936, she wandered into a bar in Key West, Fla., and met Hemingway. They drank, became friends and, the next year, when she showed up in Madrid, she picked up again with Hemingway and other war correspondents. She married the author in 1940, becoming his third wife.

They traveled and worked together, living between conflicts at a villa in Cuba. In 1945, Ms. Gellhorn left Hemingway, walking out after an argument at London's Dorchester Hotel. She was the only one of Hemingway's wives to leave him, and he never forgave her. ''His hatred of her was a terrible thing to see,'' one Hemingway biographer noted. She left, she said, because he was jealous and bullying.

Ms. Gellhorn's third marriage, to T. S. Matthews, an editor at Time magazine, also ended in divorce. She said she just found married life too boring.

After World War II, Ms. Gellhorn adopted a son in Italy and raised him, largely on her own, in Mexico and other countries, where she supported herself with a string of articles for women's magazines.

She is survived by her son, George Alexander Gellhorn of London, and a brother, Alfred Gellhorn of New York.

Ms. Gellhorn had decided that she could no longer live in the United States, and moved from Cuba to Italy to Mexico to Kenya until finally settling in Britain, where she spent her last 15 years shuttling between a small cottage in Wales, an apartment in London and the world's trouble spots. Her South Kensington apartment became a kind of salon for writers and foreign correspondents.

Bill Buford, the fiction editor at The New Yorker who was previously the editor of Granta, an English literary magazine, wrote about Ms. Gellhorn and her work: ''Reading Martha Gellhorn for the first time is a staggering experience. She is not a travel writer or a journalist or a novelist. She is all of these, and one of the most eloquent witnesses of the 20th century.''

She also wrote a highly regarded travel book in 1979, ''Travels With Myself and Another,'' that was an often humorous recounting of some of her more uncomfortable jaunts to remote corners of the globe, some with Hemingway, whom she referred to only as Unwilling Companion.

Her first love continued to be a crusading brand of nonfiction. ''Journalism is education for me,'' she wrote. ''Writing is payment for the chance to look and learn.''

She wrote on an old, battered typewriter and had to quit in 1992 when a cataract operation left her with diminished eyesight. She could no longer see the keys and felt she was too old to learn how to dictate.

But she never lost her bite. She chain-smoked, drank and ate what she pleased. ''It bores me, all that health stuff,'' she said. She told one woman who came to interview her late in life that she had to stop. ''This conversation is so boring I think I'm going to faint,'' she said.

Ms. Gellhorn had little use for most war reporting after the Vietnam War, saying that the press' role in ending that conflict had taught military leaders a lesson.

''They realized the power of the press and have been controlling it ever since,'' she said. ''Look at the Gulf War. If you wanted to go out and say to a soldier, 'How is it, kid?,' you had to bring a minder so the kid says nothing.

''It seems to me that they feed war reporters at these ridiculous briefings in the ballroom of hotels miles from anywhere.'' The public, she said, needs to realize that it is not getting the full story.

Looking back on a life that was colorful enough for any novel or reportage, Ms. Gellhorn once confessed: ''I'm overprivileged. I've had a wonderful life. I didn't deserve it but I've had it.''