Jay Hunt, the BBC1 controller, has been named as the new chief creative officer of Channel 4. She will oversee all the channel's programming when she takes up the job next year.
Ms Hunt has overseen programming on BBC1 for two-and-a-half years, and commissioned programmes such as Luther, Sherlock and Bang Goes the Theory.
Previously she had worked as director of programmes at Five, and editor of BBC1's 1pm and 6pm news bulletins.
Industry speculation had been growing that Ms Hunt would be offered the newly-created role. Channel 4 said she had been appointed following a global search.
David Abraham, Channel 4's chief executive said she would bring "ambition and experience" to the job.
"Channel 4 requires a fearless creative leader to help steer us through our next phase and Jay has demonstrated across a variety of public service genres, as well as in commercial television, her appetite to challenge the status quo, create and lead change, and promote new talent," he said.
Julian Bellamy, who had worked as acting chief creative officer and had applied for the job, will now leave the channel after a short transition period.
Mr Abraham said: "Julian has done a great job in helping refresh our schedules in recent months and I would like to thank him and acknowledge his outstanding service to Channel 4, both during my short time here so far and over the several years prior to that.
He said the recent 2010 channel of the year title, which was awarded to Channel 4 last month by industry executives, was a "fitting recognition of his efforts".
Speculation will now focus on Ms Hunt's replacement at the BBC - with BBC3 controller Danny Cohen being linked to the role.
In an email to BBC staff, the corporation's director of vision Jana Bennett praised Ms Hunt's contribution: "Jay has led BBC One with commitment and creative flair."
She said Ms Hunt had led her team with "energy, passion and a real focus on public service broadcasting".
Ms Bennett continued: "I know that this has been a difficult decision for her, but I know that Jay will bring her passion for public service broadcasting to her new role at Channel 4."
Channel 4's announcement came on the day Sir Michael Lyons announced he would step down as chairman of the BBC Trust when his term concludes next May.