Winfrey said Friday that her decision to end "The Oprah Winfrey Show" came "after much prayer and careful thought."
Thanking viewers for inviting her into their living rooms over the years, the 55-year-old Winfrey said at the end of today's live broadcast that when the show started in 1986, she was nervous and never could have imagined the "yellow brick road of blessings" that led her to this moment.
"You, our viewers, have enriched my life beyond all measures," Winfrey said as her voice cracked.
Winfrey said the reasons she plans to end the show is only because it's the right time to do so.
"I love this show, this show has been my life, and I love it enough to know when it's time to say goodbye," she said. "Twenty-five years feels right in my bones and it feels right in my spirit."
Once a local Chicago morning program, the production evolved into U.S. television's top-rated talk show for more than two decades, airing in 145 countries worldwide and watched by an estimated 42 million viewers a week in the U.S. alone.
"Oprah Winfrey is in a category of her own," said Robert Thompson, professor of television and popular culture at Syracuse University. "This is a great American story and like any great American story it's super-sized."
A spokeswoman for Winfrey's company, Harpo Productions Inc., declined to comment Thursday on Winfrey's plans except to say that "The Oprah Winfrey Show," which has seen ratings slip 7 percent from a year ago, will not move to cable television.
Winfrey, 55, is widely expected to start up a new talk show on OWN: The Oprah Winfrey Network, a much-delayed joint venture with Discovery Communications Inc. that is projected to debut in 2011. OWN is to replace the Discovery Health Channel and will debut in some 74 million homes. An OWN spokeswoman declined comment Thursday.
CBS Television Distribution, which distributes "The Oprah Winfrey Show" to more than 200 U.S. markets, held out hope it could continue doing business with Winfrey, perhaps producing a new show out of its studios in Los Angeles.
"We know that anything she turns her hand to will be a great success," the CBS Corp. unit said in a statement. "We look forward to working with her for the next several years, and hopefully afterwards as well."
Many fans heading into Harpo Studios on Friday morning seemed to support Winfrey's decision to end the show.
Said Sandra Donaldson, 59, of Indianapolis: "It's time to elevate to something new. Whatever she does is going to be a blessing. It's going to be rewarding and eye-opening. Her name alone opens doors."
Fans expressed hope that Winfrey would announce another project on Friday.
"Oprah, she impacts everybody, her life, the way she gives," Shawana Fletcher, 29, of Chicago, said outside Harpo Studios. "I hope she's not totally done. That's what we're praying."
Winfrey's 24th season opened this year with a bang, as she drew more than 20,000 fans to downtown Chicago for a block party with the Black Eyed Peas. She followed with a series of blockbuster interviews - Mike Tyson and Evander Holyfield, singer Whitney Houston and just this week, former Alaska governor and Republican vice presidential candidate Sarah Palin.
Her show's coverage has ranged from interviews with the world's celebrities to an honest discussion about Winfrey's weight struggles.
In 1986, pianist-showman Liberace gave his final TV interview to Winfrey, just six weeks before he died. In a 1993 prime-time special, Michael Jackson revealed he suffered from a skin condition that produces depigmentation. Tom Cruise enthusiastically declared his affection for the much-younger Katie Holmes on the program in 2005 - and jumped on the studio's couch to prove it.
In 2004, Winfrey unveiled her most famous giveaway, when nearly 300 members of the studio audience opened a gift box to find the keys to a new car inside. The stunt became a classic show moment as much for Winfrey's reaction - "You get a car! You get a car! You get a car! Everybody gets a car!" - as its $7 million price tag.
The show also became a launching pad for Oprah's Book Club, which then launched best-sellers. The titles ranged from "Song of Solomon" and "Paradise" by African-American writer Toni Morrison to Holocaust survivor Elie Wiesel's "Night."
For others, the selection backfired. "A Million Little Pieces" exploded in sales after Winfrey chose the James Frey memoir in fall 2005. Soon after, it was revealed as a fabricated tale of addiction and recovery, and Winfrey later chewed out Frey on her show.
"I call her 'Queen of the New Consciousness' because she did so many things to change lives, the books that she promoted," said hip-hop mogul Russell Simmons.
The loss of "The Oprah Winfrey Show" would be a blow to CBS Corp., which earns a percentage of hefty licensing fees from TV stations that use it - largely ABC network affiliates. CBS Chief Executive Leslie Moonves told analysts two weeks ago that any negative impact won't hit the company until 2012.
Winfrey started her broadcasting career in Nashville, Tennessee, and Baltimore, Maryland, before relocating to Chicago in 1984 to host a local television station's morning talk show "A.M. Chicago" - which became "The Oprah Winfrey Show" one year later. She set up Harpo the following year and her talk show went into syndication.
She also appeared in a few films, most notably in "The Color Purple," for which she received an Academy Award nomination for Best Supporting Actress.
Powered by the show's staggering success, Winfrey built a media empire. Harpo Studios produces shows hosted by Dr. Phil McGraw and celebrity chef Rachael Ray. O, The Oprah Magazine was the 7th most popular magazine in the U.S. in the first half of 2009.
"I came from nothing," Winfrey wrote in the 1998 book "Journey to Beloved." "No power. No money. Not even my thoughts were my own. I had no free will. No voice. Now, I have the freedom, power, and will to speak to millions every day - having come from nowhere."
In 2003, Winfrey became the first black woman to make Forbes magazine's billionaire's list, and just the second African-American after BET cable network founder Robert Johnson. Earlier this year, Forbes scored her net worth at $2.7 billion.
The Oprah Winfrey Leadership Academy for Girls, which cost her $40 million, opened near Johannesburg, South Africa, in 2007.
Winfrey also famously wept at the victory celebration in Chicago's Grant Park on the night last November when Barack Obama, whom she endorsed, was elected the first black U.S. president.