Oprah Winfrey is expected to officially announce that her powerhouse daytime television show will end its 25-season run in 2011.

Her production company, Harpo Productions, says Winfrey plans to announce the final date during a live broadcast Friday.

"The Oprah Winfrey Show" began as a Chicago morning program but evolved into a multibillion-dollar media empire.

It has been television's top-rated talk show for more than two decades. The show airs in 145 countries worldwide and is watched by an estimated 42 million viewers a week in the U.S. alone, though its ratings have slipped 7 percent from a year ago.

A Harpo spokeswoman declined comment Thursday on Winfrey's future plans except to say her show will not move to cable television.