(CNN) -- Oprah Winfrey will announce on Friday's "The Oprah Winfrey Show" that she is ending the talk show after 23 years, a spokesman for Winfrey's Harpo Productions said.
"Oprah will be ending her talk show," Harpo spokesman Don Halcombe said Thursday. "She will be speaking about it on tomorrow's live show."
The show will air live from its Chicago, Illinois, studio at 9 a.m. CT (10 a.m. ET), he said.
The show has been the highest-rated talk show for 23 consecutive seasons, according to the Oprah.com site. It is seen by an estimated 42 million viewers a week in the United States and is broadcast to 145 countries.
The show had its origins in 1984, when Winfrey moved to Chicago to host WLS-TV's morning talk show, "AM Chicago," which became the number-one local talk show, surpassing ratings for "Donahue," one month after she began, the site said. Within a year, it had expanded to an hour-long format and been renamed "The Oprah Winfrey Show." It entered national syndication in 1986.
In August 2004, Winfrey signed an extension for the show to keep it on the air through 2011. The status of that extension was not clear Thursday.
Over the years, the show has made news on several occasions. In September 2004, for instance, Winfrey began a new season by giving each member of the audience a new car. In May 2005, Tom Cruise caused a sensation when he jumped up and down on Oprah's couch during a declaration of love for Katie Holmes.
Other guests have shared their personal struggles, such as Elizabeth Edwards, wife of former vice presidential candidate John Edwards; performer Whitney Houston and Lisa Niemi, widow of actor Patrick Swayze.
