Gray says Channel 4 News is "a very special place to work with a special gravitational pull"Credit: Channel 4
According to an announcement by Channel 4 News, Gray started as editor in December 1997, having spent six months as deputy editor.
"I’ve enjoyed nearly a decade and a half of what I truly believe is the best job in this business," Gray said in a release.
"The programme is in fantastic shape, produced every day by an incredible team and it's time to let someone else take the reins and have the fun.
"This is a very special place to work with a special gravitational pull. Channel 4 News feels like 'home' for a certain type of person – people with journalistic passion who have something to say, and who are up for trouble-making.
"They've kept me exhilarated over the years, and that makes it very hard to say goodbye. Whilst I'm sad to do so I'm also excited about what else is out there."
Gray joined Channel 4 from the BBC where he worked for 17 years, including roles within Radio 4 and Newsnight.
According to Channel 4, the past year "has seen the most significant period of change in the programme’s history" with Gray having "led the process that introduced a new programme look, format and studio" last year "and a raft of big names to the flagship 7pm bulletin".
In May last year Channel 4 News announced that political correspondent Cathy Newman would join as a regular presenter, with other new recruits including BBC World News America anchor Matt Frei as Washington correspondent and Newsnight correspondent Jackie Long as social affairs editor.
Gray will help in the hunt for his replacement in the coming months, which the broadcaster said will run as an "open recruitment process, coordinated by Robert Lindsay Associates".
Channel 4 News presenter Jon Snow said in the announcement: "Jim Gray is the spirit and inspiration that is Channel 4 News.
"Maverick, anarchic, strict, mildly permissive, imaginative – there is no better editor in the United Kingdom.
"Jim has lived in my head for fifteen fabulous years – chucking the furniture of my certainties about, throwing many particularly treasured pieces out of the window altogether. Channel 4 News is what it is because of Jim."
ITN chief executive John Hardie added: "Jim has led an extraordinarily successful period in Channel 4 News' history – not least the last year which has seen him evolve the line-up, structure and visual identity of the show. I am incredibly grateful to him for his contribution to the programme and to ITN, and pleased that he will continue to lead the team, and advise us as we look to fill this once in a generation role."