Andrew Neil is launching a 24-hour, TV channel to rival rolling news from the BBC and Sky.
The broadcaster will be the face and chairman of GB News, signalling the end of his relationship with the BBC, where he has been one of the most respected political interviewers.
Plans are in place for "Britain's news channel", aimed at those who feel "underserved and unheard by their media", to launch early next year.
The channel could shake up the TV news landscape, currently dominated by Sky News and BBC News.
As well as being appointed chairman, broadcaster and former Sunday Times editor Neil, 71, will host a flagship evening programme in primetime, leading the programming line-up.
He said: "GB News is the most exciting thing to happen in British television news for more than 20 years.
"We will champion robust, balanced debate and a range of perspectives on the issues that affect everyone in the UK, not just those living in the London area."
Neil, best known for The Andrew Neil Show, as well as This Week and Daily Politics on the BBC, added: "We've seen a huge gap in the market for a new form of television news.
"GB News is aimed at the vast number of British people who feel underserved and unheard by their media."
The BBC confirmed this summer that Neil's self-titled show would not return to TV screens after it came off air during the pandemic.
It said at the time it was in discussions about a new interview series with Neil.
The BBC thanked Neil for his work at the corporation and wished him luck in his new role.
A statement said: "We'd like to give our heartfelt thanks to Andrew for his many years of work for the BBC, during which he's informed and entertained millions of viewers.
"From his early broadcasting days on Despatch Box in the 1990s to his recent forensic and agenda-setting political interviews, he has proved a formidable and hugely talented broadcaster.
"For years, he was at the heart of the irreverent and much-loved This Week and played a key role in the Daily and Sunday Politics, Politics Live and the BBC's general election coverage.
"We wish Andrew every success in his new role; we're sorry the US election coverage will be his last BBC presentation work for the foreseeable future but he will always be welcome at the BBC."
In a statement posted on Twitter, Neil said he left the BBC with "no animosity or desire to settle scores".
He said: "With heavy heart I announce I will be leaving the BBC.
"Despite sterling efforts by new DG to come up with other programming opportunities, it could not quite repair damage done when Andrew Neil Show cancelled early summer + Politics Live taken off air.
"But I leave with no animosity or desire to settle scores. I look back on my 25 years doing live political programmes for the BBC with affection.
"And gratitude for brilliant colleagues at Millbank, who always made sure I went into the studio fully briefed and equipped for the fray.
"They were/are the best of the best. If they can make me look good, they can make anybody look good."
Neil also responded to the BBC's statement, saying he departed with a "tear in my eye".
The political interviewer and publisher recently dismissed speculation that he was in the running to be the next BBC chairman, saying on Twitter that he has "no interest in the job".
At a time when the BBC and commercial media companies are cutting jobs, GB News said it hopes to create at least 120 positions.
They include more than 100 journalists in England, Wales, Scotland and Northern Ireland with the channel, in which global media and entertainment company Discovery, Inc is the lead investor.
GB News will feature more than 6,500 hours of content a year, made exclusively for the channel, which has secured broadcasting licences from Ofcom.
It has been founded by media executives Andrew Cole and Mark Schneider.
They said: "Andrew Neil epitomises what GB News is all about.
"He's an exceptional journalist, brilliant interviewer and fearlessly independent."
They plan for the channel to reach 96% of British television households via Freeview, Sky and Virgin Media.
GB News will broadcast seven days a week across the UK and Ireland and will be available globally on GB News digital platforms.
Sky launched a 24-hour news channel in 1989 and the BBC followed, in the UK, in 1997.
Former Sky News executive editor John McAndrew will be director of news and programming and ex-Sky News Australia chief executive Angelos Frangopoulos has been appointed chief executive officer.
GB News said that more announcements will be made in the coming weeks.
Media mogul Rupert Murdoch is also said to be planning the launch of a TV station.
Reporting by PA