Andy Duncan was previously marketing director at the BBC
Channel 4's chief executive Andy Duncan is to resign before the end of the year, it has been announced.
Mr Duncan, who has been in the post since 2004, said it was "an appropriate moment to hand on the baton to someone else and move on to a fresh challenge".
He said he would spend his remaining months in charge "securing the best possible future" for the broadcaster.
Mr Duncan had to deal with the row prompted by alleged racist bullying in 2007's Celebrity Big Brother.
He also announced the reality show would be shown for the last time on Channel 4 next year.
Mr Duncan said announcing his resignation in advance would give "a period of stable leadership" and put an end to "the distracting speculation of recent weeks".
Torin Douglas, Media correspondent
Channel 4 won awards, audiences went up and so did its share of advertising. But that wasn't enough to keep Andy Duncan in his job.
Like all commercial broadcasters, Channel 4 has been hit hard by the slump in advertising and the move to the internet - and Mr Duncan's strategy was knocked off course.
Ambitious plans to move into commercial radio and compete with BBC networks had to be abandoned, and he then asked the government for financial help.
That led to talks about a tie-up with BBC Worldwide, still unresolved.
The transition would allow Channel 4's board to recruit a successor, he added.
Mr Duncan took charge of the broadcaster at the height of its success with popular shows including Big Brother and Wife Swap.
He is known for his informal style, and wore a casual polo shirt when he publicly defended Channel 4's handling of the Celebrity Big Brother racism row.
His tenure has also seen a funding crisis at Channel 4, prompted by fall in advertising revenue, and a quest to gain the public service broadcaster a slice of the BBC's licence fee.
"Channel 4's future as a public service network is far more secure now than it was when I took over," Mr Duncan said.
Duncan also led Channel 4 into the multi-media age with the launch of digital stations including More4.
His previous jobs include marketing director at the BBC and overseeing the launch of Freeview.