TV star Susanna Reid said she could not turn down the "huge opportunity" after quitting the BBC Breakfast sofa to join ITV's new rival morning show.
The presenter - who was absent from the BBC1 show this morning and will not be returning - said her move to the newly-named breakfast show Good Morning Britain was "a really exciting challenge".
ITV's announcement earlier came after days of speculation about the 43-year-old's departure and the axing of its struggling show Daybreak.
It also follows confirmation that the mother-of-three - who has been hugely popular with the BBC audience - had split from her long-term partner Dominic Cotton.
In a statement tonight, Susanna said: "To be asked to join the next chapter of a new breakfast show is a huge opportunity for me and a really exciting challenge that I couldn't turn down.
"I am really looking forward to joining the team at Good Morning Britain later this year. I have had a fantastic time at BBC Breakfast and would like to thank everyone there. I shall miss you all lots."
Susanna also took to Twitter to thank followers for their messages of support, adding: "As a news journalist & presenter I couldn't turn down this opportunity and a new challenge."
She will be joined on Good Morning Britain by former GMTV star Ben Shephard, Charlotte Hawkins and Sean Fletcher.
Susanna, a Strictly Come Dancing finalist, has previously dismissed reports of a move to ITV, saying: "If you cut me open I would bleed BBC", but her signing was confirmed by ITV director of daytime Helen Warner this morning.
The TV boss said the new show would have an emphasis on news.
"ITV has a first-class roster of breakfast and daytime talent, both on and off screen, and I'm thrilled to be expanding this," Ms Warner said.
"Our overriding aim is to continue to improve our breakfast programming for our viewers, and we have been working for some time behind the scenes developing the next chapter of our offering.
"Engaging, news-driven content is our number one priority and will be at the heart of everything we do on Good Morning Britain. I believe we have a top team in place to deliver this and make this a compelling proposition to wake up to in the morning."
The announcement is the latest attempt by ITV to compete against BBC Breakfast since Daybreak launched, with much fanfare, in 2010.
Launch presenters Adrian Chiles and Christine Bleakley were dropped a little over a year after the programme, which replaced GMTV, first went on air.
It was later given an overhaul, with former Walking In The Air singer Aled Jones and Lorraine Kelly fronting the programme.
But with around one million viewers, Daybreak has lost out in the ratings battle to BBC Breakfast, which has pulled in around 500,000 more.
Meanwhile, Susanna's profile on BBC Breakfast increased following the departure of Sian Williams when the show moved from London to Salford in 2012.
She was later named the most popular BBC breakfast host of all time.
While her outfits won her plenty of male admirers, the presenter also raised eyebrows for occasionally "showing too much leg or cleavage".
But she hit back, saying that the focus on women in TV was a "fact of life" and added: "People seem to be shocked that women have breasts. There'll be complaints about the fact that there is literally a shadow showing."
She also dismissed the Twitter frenzy caused by her "flirty" interview with Arctic Monkeys frontman Alex Turner, calling it a "fuss about nothing".
Her profile increased further with Strictly, when she came second to Abbey Clancy, but fellow competitor Fiona Fullerton claimed Susanna had approached the BBC1 dancing show "with a PR campaign driven with military precision".
Susanna, whose big break came while she filled in for an absent presenter while working as a reporter on BBC News 24, was reportedly offered £1 million, said to be four times more than her current salary, to move to ITV.
Her new job will mean the end of her long commute from London to Salford, a journey which she has previously described as "liberating", adding: "It genuinely works for me."
Susanna's split from her partner and the father of her three young sons was confirmed when he was spotted on a dating website, where he was listed as "separated" and looking for a woman aged 35 to 45.
Daybreak host Aled will now present a new weekend morning show, Weekend, while co-host Lorraine will continue to front her own show, Lorraine, between 8.30am and 9.25am.
Charlotte is best known for Sky News show Sunrise, while Sean comes from Sky Sports and all four will join the channel as ITV's main weekday presenters, between 6am and 8.30am.
The BBC confirmed Susanna will not be returning to the Breakfast sofa ahead of her ITV debut.
Adam Bullimore, the editor of BBC Breakfast, said: "BBC Breakfast is a hugely successful programme and Susanna has been part of that. We are sorry she's decided to leave and wish her the best for the future."
Ben will be returning to the early morning beat on ITV four years after leaving GMTV.
He said: "Having an intimate knowledge of broadcasting at this time of the morning I know there's nothing quite like it. After a four-year lie-in, I've dusted off the alarm clock, bought a new coffee machine and I can't wait to get started with the rest of the Good Morning Britain team."
Ben will continue to appear on Sky Sports, alongside his role on the ITV programme.
"Anyone who knows me knows that football and sport are major passions of mine. I love being a part of Sky Sports and I am really looking forward to continuing to host Goals on Sunday, a programme that is extremely close to my heart."
The latest revamp revives the name which was used by the station's morning show when it launched a breakfast TV service in 1983.