The BBC has also announced that Victoria Derbyshire is to become joint lead presenter on Newsnight.
Kay, 52, will now be on the show from Monday to Wednesday and will start his role immediately.
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Derbyshire, who will be joint lead presenter with Kirsty Wark, will take on her position in September.
Kay, who has previously filled in on the programme, said: “I’m over the moon to become the new regular presenter of BBC Breakfast and I’m looking forward to bringing our brilliant viewers the very latest news each morning alongside my good friend Sally (Nugent) and the rest of the team.
"Sitting on the famous red sofa is a real privilege while covering the stories and issues that matter to our audience – home and abroad.”
Derbyshire, 53, said she was "so delighted to be joining the legend that is Kirsty Wark and the talented Newsnight team under new and ambitious leadership".
"This is a special opportunity to take on one of the best jobs in British journalism and help shape the programme’s future," she said.
"I can’t wait to champion more stories about people’s lives while holding those who represent them to account.”
Jonathan Munro, Interim Director of BBC News, said: “It’s fantastic to be appointing two such talented presenters to start and finish the day on two of our most important news programmes."
He went on: "Jon’s a hugely experienced journalist who’s established himself as a favourite with BBC Breakfast viewers, and Victoria’s a formidable interviewer with an amazing connection to her audiences.
We are delighted to announce two new appointments:
⭐️Jon Kay is appointed @BBCBreakfast presenter
⭐️Victoria Derbyshire is appointed @BBCNewsnight presenter
Read more: https://t.co/wOHKtoU0wf pic.twitter.com/ycbWpUKXN2
— BBC News Press Team (@BBCNewsPR) July 8, 2022
"Congratulations to both of them.”
BBC Breakfast editor Richard Frediani called Kay "a brilliant broadcaster who can turn his hand to hard-hitting news stories, celebrity interviews and everything in between".
Newsnight editor Stewart Maclean said Derbyshire was "one of the most tenacious journalists in the business".
"We’re delighted she’s joining us on Newsnight as a lead presenter alongside Kirsty," he said, adding that they would be "a formidable partnership".
Derbyshire will also continue to present Ukrainecast on BBC Sounds.
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