BBC Three controller Zai Bennett has announced he is leaving the BBC, a month after it was revealed his channel would be scrapped and moved online.
Bennett, who joined the corporation in 2011, has commissioned some of BBC Three's biggest hits, including The Call Centre and comedy Bad Education.
He had previously been at ITV, where he was responsible for Celebrity Juice and The Only Way Is Essex.
After leaving the BBC in June, he will become director of Sky Atlantic.
"Zai has been a fantastic Controller of BBC Three and has led the Channel to great success," said the BBC's director of television, Danny Cohen.
"He's a true gentleman and I will miss working with him."
BBC Three is to close as an on-air channel in autumn 2015. The BBC says it will save millions by cutting the channel's programme budget from £85m to £25m.
The channel will continue to have a home on the iPlayer, with some of its programmes aired later on BBC One and BBC Two.
Director general Tony Hall called the plan "financially necessary" and said £30m of the savings would be reinvested in BBC One drama.
Mr Bennett, whose BBC salary was £219,900, admitted he had been "shocked" by the decision to close BBC Three.
"It's more popular than Channel 4 for 16-24 year olds and from 22:00 each evening, it is the biggest channel for 16-34s bar none," he wrote on the BBC website.
"BBC Three is also the only channel in the UK that makes documentaries and current affairs specifically for the young adult audience."
In his new role, the 39-year-old will oversee Sky's portfolio of HBO programmes, including Game of Thrones, True Detective and Mad Men.
Sky Atlantic has also committed to commission at least six UK programmes per year, with recent hits including the Alan Partridge series Mid Morning Matters.
Mr Bennett said joining Sky Atlantic was an opportunity he "couldn't turn down", calling it "one of the best jobs in the industry".
He added: "I will miss working with the outstanding channel and commissioning teams.
"The BBC is lucky to be home to some of the most creative and inspiring people in television and it's been a privilege to learn from them in my time here."
Sky's Stuart Murphy said: "Zai has huge experience in commercial TV and his innate desire to welcome and support creative risk is a perfect fit for Sky.
"With his new role at Sky Atlantic, we will give him the backing and platform to do this at an epic scale."
Responsibility for defining the new look of BBC Three has been passed to Damian Kavanagh, who is head of the BBC's daytime TV output.