CNN Worldwide President Jim Walton said on Friday that he was leaving the once-dominant cable news network, which has struggled in the ratings in recent years, on December 31.
A search will begin immediately for a new president, the network said.
"CNN needs new thinking. That starts with a new leader who brings a different perspective, different experiences and a new plan," Walton, who had been president of CNN since 2003, said in a memo.
CNN, which is owned by Time Warner Inc, has tried to hold the middle ground in its news coverage, a position that some blame for its ratings erosion, while ratings have risen for Fox News and MSNBC, which combine news with opinion and political commentary.
For the second quarter, CNN posted its weakest primetime ratings in 21 years, while its total viewers also fell 35 percent from a year earlier.