That was followed by a confirmation via press release from the President of Harpo, Tim Bennett.

He said, “Tomorrow, Oprah will announce live on ‘The Oprah Winfrey Show’ that she has decided to end what is arguably one of the most popular, influential and enduring programs in television history. The sun will set on the ‘Oprah’ show as its 25th season draws to a close on September 9, 2011.”

Oprah Winfrey, the daytime talk show host whose media empire also includes a television production company, radio show, magazine, popular Web site and other ventures, will soon be getting her own television network.

Ms. Winfrey and Discovery Communications said on Tuesday that they would jointly create OWN, the Oprah Winfrey Network, a cable television channel to make its debut in 2009 on what is now the Discovery Health Channel. Discovery Health is available in more than 70 million homes.

The new channel will not initially carry “The Oprah Winfrey Show,” the top-rated syndicated daytime talk show featuring Ms. Winfrey as host. But Ms. Winfrey said that she had the option to end that show in 2010 or 2011 and could move the talk show to the new channel then.

“Eventually that will happen, we hope,” Ms. Winfrey said in a conference call with reporters on Tuesday.

The venture will be half owned by Discovery, of Silver Spring, Md., and half by Harpo Inc., Ms. Winfrey’s production company, which is based in Chicago. Ms. Winfrey will serve as chairwoman of the network, will have full editorial control over the joint venture and will be responsible for its “programming, branding and creative vision,” the companies said.

In addition to continuing her syndicated talk show, Ms. Winfrey said she would also continue to produce programming for other outlets. A new reality show, “Oprah’s Big Give,” is scheduled to begin on ABC in March.

Discovery and Harpo said the new venture involved no additional cash investment, but that Ms. Winfrey would contribute her Oprah.com Web site to the company. This is not Ms. Winfrey’s first foray into television programming. She was an initial investor in the Oxygen cable channel in 1998, but she soon cut many of her ties to that company.

Asked about the difference between Oxygen, which was sold to NBC in October for $925 million, and the latest venture, Ms. Winfrey said Oxygen “did not reflect my voice.” That assertion is subject to interpretation, however; Ms. Winfrey was host of a 12-part series called “Oprah Goes Online” on Oxygen. The show was sort of a primer on the Internet. She also was frequently referred to as a co-founder of the channel in news reports at the time.

“I was not a participant in the development of the channel,” she said. “That’s why after a couple of board meetings I took myself off the board.”

With the Oprah Winfrey Network, “I will have editorial control,” she said. “I have a vision for what we want to accomplish with this network.”

David Zaslav, president and chief executive of Discovery Communications, said that he and Ms. Winfrey would immediately begin a search for a chief executive for the Oprah Winfrey Network.