She drew criticism after barely challenging Marion Jones when the former sprinter claimed in an interview in 2008 to have had no knowledge of her own doping.
The American had just served a six-month prison sentence for her part in the Balco scandal.
"I didn't love myself enough to tell the truth," Jones confessed. "I'm trying to move on. I hope that everybody else can move on, too."
The following year, Mike Tyson broke down as he told Winfrey about the accidental death of his 4-year-old daughter, and apologised for biting off part of boxing rival Evander Holyfield's ear in their notorious 1997 "bite fight".
Winfrey's warmth and reach have tempted Michael Jackson and the Duchess of York, among others, to reveal perhaps more than they had planned, and her talk show has been praised and criticised for unleashing a culture of confession that won her millions of fans.
The "Oprah-fication" of American life, as the Wall Street Journal called it, has also been observed beyond the glare of the presenter's studio lights, in the "emoting" of public figures and even presidents.
But Winfrey has struggled to maintain her influence since she quit her show in 2011 to launch the Oprah Winfrey Network (OWN), which has suffered from declining viewing figures and management shake-ups.
She was rumoured to be pursuing Tiger Woods before the golfer made his own televised statement four months after revelations about his infidelity.
Armstrong may be a bigger and much-needed ratings coup.
OWN announced the interview yesterday. But it added nothing about the extent of any confession or the timing of the conversation, which will be broadcast on television and online in the early afternoon (NZ time) of January 18.
Few are holding their breath in expectation of a full mea culpa.
"Armstrong has defended himself with tooth and nail for decades," said the cycling commentator for Britain's ITV, Ned Boulting. "To dent his reputation in front of a global audience would represent a complete about- face in the way he operates.
Armstrong's lawyers will pay closest attention to the interview. The cyclist is already facing lawsuits filed by some of the accusers he sought to silence. If he can navigate legal pitfalls while appearing contrite, he could flourish before a typically forgiving audience.
"Oprah appeals to that deep part of middle America that to some extent still wants to believe in legends," Boulting said. "There are still people on Armstrong's side and those who are swayable to his cause ... Oprah is perfect."
Armstrong has shown little sign of contrition since he was stripped of his titles in October. In November, he tweeted a photo of himself lying on his sofa surrounded by his framed Tour de France jerseys.
This week he changed his profile on Strava, a popular fitness website, to read: "According to my rivals, peers, and teammates I won the Tour de France 7 times."
- Independent, additional reporting: AFP
