Janine Gibson, editor-in-chief of The Guardian website and a deputy editor of Guardian News and Media, is leaving the title after 17 years.
Gibson's departure comes shortly after she failed in a bid to replace Alan Rusbridger as editor-in-chief of Guardian News and Media.
She was among 26 people to apply for the job, and four to take part in a hustings event for a staff ballot. Kath Viner, who replaced Gibson as editor of The Guardian US last summner, won the hustings – claiming 438 first-choice votes, 53 per cent of the total cast – and was later named as Rusbridger's successor.
Gibson, who launched The Guardian's media website and was previously Media Guardian editor, came third – behind Emily Bell – with 175 votes.
Gibson started her career in journalism at Televisual, first as a staff writer and then rising to become deputy editor, before moving on to Broadcast magazine in July 1997. She then went on to become media correspondent for The Independent before joining The Guardian in 1998.
She was at the helm of Guardian US for the newspaper group's coverage of the NSA-Snowden stories.
According to a staff email, published by Guido Fawkes, The New York Times "tried to poach her to be their deputy editor early last year", but added that "we managed to keep her".
A Guardian spokesman said: "We can confirm that Janine Gibson is leaving The Guardian. It is entirely amicable and we wish her the very best for the future."