The media mogul Oprah Winfrey will end her daytime talk show, “The Oprah Winfrey Show,” in 2011 as she prepares to start a cable channel of her own.

Larry Downing/Reuters

A spokeswoman for Ms. Winfrey’s production company, Harpo, confirmed Thursday evening that Ms. Winfrey would make an announcement on her show on Friday. The plans were first reported by WABC, the ABC station in New York City.

“The sun will set on the Oprah show as its 25th season draws to a close on Sept. 9, 2011,” Tim Bennett, the president of Harpo, said in a message to affiliates.

After her broadcast talk show winds down, Ms. Winfrey will concentrate on her coming cable channel, OWN: The Oprah Winfrey Network. OWN will have its premiere in January 2011, according to a person with knowledge of Ms. Winfrey’s decision who insisted on anonymity.

Ms. Winfrey, 55, informed her talk show staff of her decision on Thursday afternoon. The television world had expected that she would make a decision about the fate of her program by the end of the year.

Ms. Winfrey told her staffers that she will not transfer the show to cable. She is expected to produce new programs for OWN, and may appear on some of them.

In a statement, CBS Television Distribution said, “We have the greatest respect for Oprah and wish her nothing but the best in her future endeavors. We know that anything she turns her hand to will be a great success. We look forward to working with her for the next several years, and hopefully afterwards as well.”

OWN is a joint venture between her production company and Discovery Communications. Getting the channel off the ground has proved challenging amid management turnover and an uncertain advertising climate.

The timeline for OWN will theoretically give Ms. Winfrey about nine months to promote her cable channel on her existing show.

Sometimes called the Queen of Talk, Forbes estimates Ms. Winfrey’s net worth to be $2.7 billion. “The Oprah Winfrey Show” is the most successful talk show in syndication, reaching about seven million viewers a day. It has been vital to the success of ABC, whose local station group has been the primary home of the show since it started in syndication in 1986.