The pop icon, who in the 1980s set aside the fantasy girl image to tackle serious roles, died shortly before 9:30 a.m. in a Santa Monica hospital, spokesman Paul Bloch said.
Ryan O'Neal, the longtime companion who had reunited with Ms. Fawcett as she fought anal cancer, was at her side, along with close friend Alana Stewart, Mr. Bloch said.
"After a long and brave battle with cancer, our beloved Farrah has passed away," Mr. O'Neal said. "Although this is an extremely difficult time for her family and friends, we take comfort in the beautiful times that we shared with Farrah over the years and the knowledge that her life brought joy to so many people around the world."
Ms. Fawcett burst on the scene in 1976 as one-third of the crime-fighting trio in TV's Charlie's Angels . A poster of her in a clingy swimsuit sold in the millions.
Her full, layered hairstyle became all the rage, with girls and women across America adopting the look.
She left the show after one season but had a flop on the big screen with Somebody Killed Her Husband. She turned to more serious roles in the 1980s and 1990s, winning praise playing an abused wife in The Burning Bed.
She had been diagnosed with cancer in 2006. As she underwent treatment, she enlisted the help of Mr. O'Neal, who was the father of her now 24-year-old son, Redmond.
This month, Mr. O'Neal said he asked Ms. Fawcett to marry him and she agreed, but they were unable to wed before she died.
Her struggle with painful treatments and dispiriting setbacks was recorded in the television documentary Farrah's Story . Ms. Fawcett sought cures in the U.S. and Germany, battling the disease with iron determination even as her body weakened. NBC estimated the May 15, 2009, broadcast drew nearly 9 million viewers.
In the documentary, Ms. Fawcett was seen shaving off most of her trademark locks before chemotherapy could claim them. Toward the end, she was seen huddled in bed, barely responding to a visit from her son.
Ms. Fawcett, Kate Jackson and Jaclyn Smith made up the original Angels , the sexy, police-trained trio of martial arts experts who took their assignments from a rich, mysterious boss named Charlie (John Forsythe, who was never seen on camera but whose distinctive voice was heard on speaker phone.)
The program debuted in September 1976, the height of what some critics derisively referred to as television's "jiggle show" era, and it gave each of the actresses ample opportunity to show off their figures as they disguised themselves in bathing suits and as hookers and strippers to solve crimes.
Backed by a clever publicity campaign, Ms. Fawcett -- then billed as Farrah Fawcett-Majors because of her marriage to The Six Million Dollar Man star Lee Majors -- quickly became the most popular Angel of all.
"She was an angel on Earth and now an angel forever," Mr. Majors said Thursday.
Ms. Fawcett's most unfortunate career moment might have been a 1997 appearance on David Letterman's show, when her disjointed, rambling answers led many to speculate that she was on drugs. She denied that, blaming her strange behavior on questionable advice from her mother to be playful and have a good time.
Born Feb. 2, 1947, in Corpus Christi, Texas, she was named Mary Farrah Leni Fawcett by her mother, who said she added the Farrah because it sounded good with Fawcett. She was less than a month old when she underwent surgery to remove a digestive tract tumor with which she was born.
After attending Roman Catholic grade school and W.B. Ray High School, Ms. Fawcett enrolled at the University of Texas at Austin. Fellow students voted her one of the 10 most beautiful people on the campus and her photos were eventually spotted by movie publicist David Mirisch, who suggested she pursue a film career. After overcoming her parents' objections, she agreed.
Soon she was appearing in such TV shows as That Girl, The Flying Nun, I Dream of Jeannie and The Partridge Family .
"After a long and brave battle with cancer, our beloved Farrah has passed away. Although this is an extremely difficult time for her family and friends, we take comfort in the beautiful times that we shared with Farrah over the years and the knowledge that her life brought joy to so many people around the world." -- Ryan O'Neal, longtime companion.
"She was an angel on Earth and now an angel forever." -- Lee Majors, ex-husband.
"There are no words to express the deep sense of loss that I feel. For 30 years Farrah was much more than a friend, she was my sister, and although I will miss her terribly I know in my heart that she will always be there as that angel on the shoulder of everyone who loved her." -- Alana Stewart, close friend.
"Farrah had courage, she had strength and she had faith. And now she has peace as she rests with the real angels." -- Jacyln Smith, co-star in "Charlie's Angels."
"Farrah had an outstanding talent, better than most feature film actresses that I've seen. She was great to work with and will be missed." -- Robert Duvall, director and co-star in "The Apostle."
"I'm terribly sad about Farrah's passing. She was incredibly brave and God will be welcoming her with open arms." -- Cheryl Ladd, co-star in "Charlie's Angels."
"I will miss Farrah everyday. She was a selfless person who loved her family and friends with all her heart, and what a big heart it was. Farrah showed immense courage and grace throughout her illness and was an inspiration to those around her. When I think of Farrah I will remember her kindness, her cutting dry wit and, of course, her beautiful smile. Today, when you think of Farrah, remember her smiling because that is exactly how she wanted to be remembered: smiling." -- Kate Jackson, co-star in "Charlie's Angels."
"I remember when we had dinner and she said, 'I'm going in to meet with Aaron Spelling on some new TV series about three girls who are detectives.' And the next day she told me, 'Kate Jackson and I are going to be two of them, and they're looking for the third. I set up an appointment for you.' That's the way she was: generous with her friends." -- Susie Coelho, TV personality, businesswoman and longtime friend.
"Farrah was one of the iconic beauties of our time. Her girl-next-door charm combined with stunning looks made her a star on film, TV and the printed page. I was saddened to learn of her passing earlier today and my thoughts and prayers go out to her family and friends." -- Hugh Hefner, Playboy magazine founder.