The BBC's controller of continuing drama, Mal Young, is leaving to join Pop Idol creator Simon Fuller's company 19 TV.
Eastenders is among the programmes overseen by Mr Young
Mr Young joined the BBC as head of drama series in 1997 and has overseen several programmes including EastEnders, Casualty and Holby City.
BBC creative director Alan Yentob paid tribute to the "great contribution" made by Mr Young.
He will not be leaving the BBC until the end of the year.
Mr Fuller, who runs management company 19, was the man behind enormously successful pop acts such as the Spice Girls and S Club 7 before creating Pop Idol and American Idol.
Mr Young's departure comes just a week after the executive producer of EastEnders, Louise Berridge, stepped down.
"I've had the happiest and most fulfilling seven years at the BBC, but when Simon approached me about he and I working together, it was a no-brainer," said Mr Young.
'Talk about TV'
"We both aspire to make 'talk about TV' for big mainstream audiences and the time feels right for us to take advantage of the many exciting opportunities, both in the UK and the States.
"I wasn't actively looking to leave the BBC, but this felt like the perfect fit."
Paying tribute to his departing colleague, Mr Yentob added: "Over the last seven years Mal has developed shows which bear testament to his passion and commitment to popular drama.
"He's now got a new challenge in the USA. We'll miss him but we look forward to working with him in his new role."
Jane Tranter, Controller Drama Commissioning echoed these sentiments.
She said: "Mal Young is one of television drama's best known and highly respected characters.
"There is no doubt that we shall all miss him, but his new venture is a hugely exciting opportunity.
"He will be a great success and we look forward to working with him a different capacity in the future."