Carlson received a $20 million settlement from 21st Century Fox in September.
Fired on Wednesday amid a drumbeat of sexual harassment allegations, the vacationing host's "The O'Reilly Factor" was quickly redubbed "The Factor" and Fox News announced his time slot will be filled by Tucker Carlson, another adamantly conservative Fox host who dovetails with the channel's audience.
"It is tremendously disheartening that we part ways due to completely unfounded claims", O'Reilly said.
O'Reilly said in an April 1 statement that he had been unfairly targeted because of his public prominence.
Bill O'Reilly has been forced out of his position as a prime-time host at Fox News, the company said Wednesday, after the disclosure of settlements involving sexual harassment allegations against him.
Several weeks ago, a woman named Wendy Walsh stepped forward with another complaint against O'Reilly.
"The O'Reilly Factor" lost about 90 advertisers following the report, leading 21 Century Fox to oust the television star Wednesday.
"It's a business and if the pushback... was going to hurt Fox's bottom line then he's gone", he told AFP.
But O'Reilly has been on Fox News for more than two decades.
His lawyer has come out more forcefully, however.
She recalled one incident in which O'Reilly "got Margaret's name wrong, and she said, 'Hey, get my name right.' And he said, 'Oh, I'm sorry there's a lot of blondes in this operation, I can't keep you all straight, Megyn Kelly is coming up.' He starts telling all these blonde names". This law firm has uncovered evidence that the smear campaign is being orchestrated by far-left organization bent on destroying O'Reilly for political and financial reasons. "That evidence will be put forth shortly, and it is irrefutable".
Last year, he came under fire after riffing on remarks made by first lady Michelle Obama at the Democratic National Convention that the White House was built by slaves.
"And I was told basically, "Well, you know, Bill". We have full confidence that the network will continue to be a powerhouse in cable news. Fox's longtime CEO Roger Ailes resigned abruptly amid similar sexual harassment charges last July.
For the moment, O'Reilly's lucrative publishing career does not appear to be in dire jeopardy.
As the accusations piled up, more than 50 major advertisers pulled out of his show even though viewership soared.
Investors seemed to take the news in stride.
He ended by inviting O'Reilly, 67, to come and live with him and former Daily Show host Jon Stewart in a mountain cabin.
It was a humiliating blow to one of the biggest United States media names, a veteran broadcaster at Fox News for two decades who counted President Donald Trump among his personal supporters and whose ratings soared in defiance of his alleged abusive behavior towards women. It remains unclear whether the network will allow the host to say a farewell of his own on-air.